diff --git a/lib/web/cache/cache.js b/lib/web/cache/cache.js
index 5a66d08cb6c..45c6fec3467 100644
--- a/lib/web/cache/cache.js
+++ b/lib/web/cache/cache.js
@@ -42,10 +42,12 @@ class Cache {
 
   async match (request, options = {}) {
     webidl.brandCheck(this, Cache)
-    webidl.argumentLengthCheck(arguments, 1, { header: 'Cache.match' })
 
-    request = webidl.converters.RequestInfo(request)
-    options = webidl.converters.CacheQueryOptions(options)
+    const prefix = 'Cache.match'
+    webidl.argumentLengthCheck(arguments, 1, prefix)
+
+    request = webidl.converters.RequestInfo(request, prefix, 'request')
+    options = webidl.converters.CacheQueryOptions(options, prefix, 'options')
 
     const p = this.#internalMatchAll(request, options, 1)
 
@@ -59,17 +61,20 @@ class Cache {
   async matchAll (request = undefined, options = {}) {
     webidl.brandCheck(this, Cache)
 
-    if (request !== undefined) request = webidl.converters.RequestInfo(request)
-    options = webidl.converters.CacheQueryOptions(options)
+    const prefix = 'Cache.matchAll'
+    if (request !== undefined) request = webidl.converters.RequestInfo(request, prefix, 'request')
+    options = webidl.converters.CacheQueryOptions(options, prefix, 'options')
 
     return this.#internalMatchAll(request, options)
   }
 
   async add (request) {
     webidl.brandCheck(this, Cache)
-    webidl.argumentLengthCheck(arguments, 1, { header: 'Cache.add' })
 
-    request = webidl.converters.RequestInfo(request)
+    const prefix = 'Cache.add'
+    webidl.argumentLengthCheck(arguments, 1, prefix)
+
+    request = webidl.converters.RequestInfo(request, prefix, 'request')
 
     // 1.
     const requests = [request]
@@ -83,7 +88,9 @@ class Cache {
 
   async addAll (requests) {
     webidl.brandCheck(this, Cache)
-    webidl.argumentLengthCheck(arguments, 1, { header: 'Cache.addAll' })
+
+    const prefix = 'Cache.addAll'
+    webidl.argumentLengthCheck(arguments, 1, prefix)
 
     // 1.
     const responsePromises = []
@@ -95,7 +102,7 @@ class Cache {
     for (let request of requests) {
       if (request === undefined) {
         throw webidl.errors.conversionFailed({
-          prefix: 'Cache.addAll',
+          prefix,
           argument: 'Argument 1',
           types: ['undefined is not allowed']
         })
@@ -113,7 +120,7 @@ class Cache {
       // 3.2
       if (!urlIsHttpHttpsScheme(r.url) || r.method !== 'GET') {
         throw webidl.errors.exception({
-          header: 'Cache.addAll',
+          header: prefix,
           message: 'Expected http/s scheme when method is not GET.'
         })
       }
@@ -131,7 +138,7 @@ class Cache {
       // 5.2
       if (!urlIsHttpHttpsScheme(r.url)) {
         throw webidl.errors.exception({
-          header: 'Cache.addAll',
+          header: prefix,
           message: 'Expected http/s scheme.'
         })
       }
@@ -251,10 +258,12 @@ class Cache {
 
   async put (request, response) {
     webidl.brandCheck(this, Cache)
-    webidl.argumentLengthCheck(arguments, 2, { header: 'Cache.put' })
 
-    request = webidl.converters.RequestInfo(request)
-    response = webidl.converters.Response(response)
+    const prefix = 'Cache.put'
+    webidl.argumentLengthCheck(arguments, 2, prefix)
+
+    request = webidl.converters.RequestInfo(request, prefix, 'request')
+    response = webidl.converters.Response(response, prefix, 'response')
 
     // 1.
     let innerRequest = null
@@ -269,7 +278,7 @@ class Cache {
     // 4.
     if (!urlIsHttpHttpsScheme(innerRequest.url) || innerRequest.method !== 'GET') {
       throw webidl.errors.exception({
-        header: 'Cache.put',
+        header: prefix,
         message: 'Expected an http/s scheme when method is not GET'
       })
     }
@@ -280,7 +289,7 @@ class Cache {
     // 6.
     if (innerResponse.status === 206) {
       throw webidl.errors.exception({
-        header: 'Cache.put',
+        header: prefix,
         message: 'Got 206 status'
       })
     }
@@ -295,7 +304,7 @@ class Cache {
         // 7.2.1
         if (fieldValue === '*') {
           throw webidl.errors.exception({
-            header: 'Cache.put',
+            header: prefix,
             message: 'Got * vary field value'
           })
         }
@@ -305,7 +314,7 @@ class Cache {
     // 8.
     if (innerResponse.body && (isDisturbed(innerResponse.body.stream) || innerResponse.body.stream.locked)) {
       throw webidl.errors.exception({
-        header: 'Cache.put',
+        header: prefix,
         message: 'Response body is locked or disturbed'
       })
     }
@@ -380,10 +389,12 @@ class Cache {
 
   async delete (request, options = {}) {
     webidl.brandCheck(this, Cache)
-    webidl.argumentLengthCheck(arguments, 1, { header: 'Cache.delete' })
 
-    request = webidl.converters.RequestInfo(request)
-    options = webidl.converters.CacheQueryOptions(options)
+    const prefix = 'Cache.delete'
+    webidl.argumentLengthCheck(arguments, 1, prefix)
+
+    request = webidl.converters.RequestInfo(request, prefix, 'request')
+    options = webidl.converters.CacheQueryOptions(options, prefix, 'options')
 
     /**
      * @type {Request}
@@ -445,8 +456,10 @@ class Cache {
   async keys (request = undefined, options = {}) {
     webidl.brandCheck(this, Cache)
 
-    if (request !== undefined) request = webidl.converters.RequestInfo(request)
-    options = webidl.converters.CacheQueryOptions(options)
+    const prefix = 'Cache.keys'
+
+    if (request !== undefined) request = webidl.converters.RequestInfo(request, prefix, 'request')
+    options = webidl.converters.CacheQueryOptions(options, prefix, 'options')
 
     // 1.
     let r = null
@@ -810,17 +823,17 @@ const cacheQueryOptionConverters = [
   {
     key: 'ignoreSearch',
     converter: webidl.converters.boolean,
-    defaultValue: false
+    defaultValue: () => false
   },
   {
     key: 'ignoreMethod',
     converter: webidl.converters.boolean,
-    defaultValue: false
+    defaultValue: () => false
   },
   {
     key: 'ignoreVary',
     converter: webidl.converters.boolean,
-    defaultValue: false
+    defaultValue: () => false
   }
 ]
 
diff --git a/lib/web/cache/cachestorage.js b/lib/web/cache/cachestorage.js
index de3813cfecb..cc773b94b49 100644
--- a/lib/web/cache/cachestorage.js
+++ b/lib/web/cache/cachestorage.js
@@ -20,7 +20,7 @@ class CacheStorage {
 
   async match (request, options = {}) {
     webidl.brandCheck(this, CacheStorage)
-    webidl.argumentLengthCheck(arguments, 1, { header: 'CacheStorage.match' })
+    webidl.argumentLengthCheck(arguments, 1, 'CacheStorage.match')
 
     request = webidl.converters.RequestInfo(request)
     options = webidl.converters.MultiCacheQueryOptions(options)
@@ -57,9 +57,11 @@ class CacheStorage {
    */
   async has (cacheName) {
     webidl.brandCheck(this, CacheStorage)
-    webidl.argumentLengthCheck(arguments, 1, { header: 'CacheStorage.has' })
 
-    cacheName = webidl.converters.DOMString(cacheName)
+    const prefix = 'CacheStorage.has'
+    webidl.argumentLengthCheck(arguments, 1, prefix)
+
+    cacheName = webidl.converters.DOMString(cacheName, prefix, 'cacheName')
 
     // 2.1.1
     // 2.2
@@ -73,9 +75,11 @@ class CacheStorage {
    */
   async open (cacheName) {
     webidl.brandCheck(this, CacheStorage)
-    webidl.argumentLengthCheck(arguments, 1, { header: 'CacheStorage.open' })
 
-    cacheName = webidl.converters.DOMString(cacheName)
+    const prefix = 'CacheStorage.open'
+    webidl.argumentLengthCheck(arguments, 1, prefix)
+
+    cacheName = webidl.converters.DOMString(cacheName, prefix, 'cacheName')
 
     // 2.1
     if (this.#caches.has(cacheName)) {
@@ -105,9 +109,11 @@ class CacheStorage {
    */
   async delete (cacheName) {
     webidl.brandCheck(this, CacheStorage)
-    webidl.argumentLengthCheck(arguments, 1, { header: 'CacheStorage.delete' })
 
-    cacheName = webidl.converters.DOMString(cacheName)
+    const prefix = 'CacheStorage.delete'
+    webidl.argumentLengthCheck(arguments, 1, prefix)
+
+    cacheName = webidl.converters.DOMString(cacheName, prefix, 'cacheName')
 
     return this.#caches.delete(cacheName)
   }
diff --git a/lib/web/cookies/index.js b/lib/web/cookies/index.js
index 1fc2bd295f6..d40c71318e5 100644
--- a/lib/web/cookies/index.js
+++ b/lib/web/cookies/index.js
@@ -24,7 +24,7 @@ const { Headers } = require('../fetch/headers')
  * @returns {Record<string, string>}
  */
 function getCookies (headers) {
-  webidl.argumentLengthCheck(arguments, 1, { header: 'getCookies' })
+  webidl.argumentLengthCheck(arguments, 1, 'getCookies')
 
   webidl.brandCheck(headers, Headers, { strict: false })
 
@@ -51,11 +51,12 @@ function getCookies (headers) {
  * @returns {void}
  */
 function deleteCookie (headers, name, attributes) {
-  webidl.argumentLengthCheck(arguments, 2, { header: 'deleteCookie' })
-
   webidl.brandCheck(headers, Headers, { strict: false })
 
-  name = webidl.converters.DOMString(name)
+  const prefix = 'deleteCookie'
+  webidl.argumentLengthCheck(arguments, 2, prefix)
+
+  name = webidl.converters.DOMString(name, prefix, 'name')
   attributes = webidl.converters.DeleteCookieAttributes(attributes)
 
   // Matches behavior of
@@ -73,7 +74,7 @@ function deleteCookie (headers, name, attributes) {
  * @returns {Cookie[]}
  */
 function getSetCookies (headers) {
-  webidl.argumentLengthCheck(arguments, 1, { header: 'getSetCookies' })
+  webidl.argumentLengthCheck(arguments, 1, 'getSetCookies')
 
   webidl.brandCheck(headers, Headers, { strict: false })
 
@@ -93,7 +94,7 @@ function getSetCookies (headers) {
  * @returns {void}
  */
 function setCookie (headers, cookie) {
-  webidl.argumentLengthCheck(arguments, 2, { header: 'setCookie' })
+  webidl.argumentLengthCheck(arguments, 2, 'setCookie')
 
   webidl.brandCheck(headers, Headers, { strict: false })
 
@@ -110,12 +111,12 @@ webidl.converters.DeleteCookieAttributes = webidl.dictionaryConverter([
   {
     converter: webidl.nullableConverter(webidl.converters.DOMString),
     key: 'path',
-    defaultValue: null
+    defaultValue: () => null
   },
   {
     converter: webidl.nullableConverter(webidl.converters.DOMString),
     key: 'domain',
-    defaultValue: null
+    defaultValue: () => null
   }
 ])
 
@@ -137,32 +138,32 @@ webidl.converters.Cookie = webidl.dictionaryConverter([
       return new Date(value)
     }),
     key: 'expires',
-    defaultValue: null
+    defaultValue: () => null
   },
   {
     converter: webidl.nullableConverter(webidl.converters['long long']),
     key: 'maxAge',
-    defaultValue: null
+    defaultValue: () => null
   },
   {
     converter: webidl.nullableConverter(webidl.converters.DOMString),
     key: 'domain',
-    defaultValue: null
+    defaultValue: () => null
   },
   {
     converter: webidl.nullableConverter(webidl.converters.DOMString),
     key: 'path',
-    defaultValue: null
+    defaultValue: () => null
   },
   {
     converter: webidl.nullableConverter(webidl.converters.boolean),
     key: 'secure',
-    defaultValue: null
+    defaultValue: () => null
   },
   {
     converter: webidl.nullableConverter(webidl.converters.boolean),
     key: 'httpOnly',
-    defaultValue: null
+    defaultValue: () => null
   },
   {
     converter: webidl.converters.USVString,
@@ -172,7 +173,7 @@ webidl.converters.Cookie = webidl.dictionaryConverter([
   {
     converter: webidl.sequenceConverter(webidl.converters.DOMString),
     key: 'unparsed',
-    defaultValue: []
+    defaultValue: () => new Array(0)
   }
 ])
 
diff --git a/lib/web/eventsource/eventsource.js b/lib/web/eventsource/eventsource.js
index 0b1e48dbd2d..51634c1779f 100644
--- a/lib/web/eventsource/eventsource.js
+++ b/lib/web/eventsource/eventsource.js
@@ -105,7 +105,8 @@ class EventSource extends EventTarget {
     // 1. Let ev be a new EventSource object.
     super()
 
-    webidl.argumentLengthCheck(arguments, 1, { header: 'EventSource constructor' })
+    const prefix = 'EventSource constructor'
+    webidl.argumentLengthCheck(arguments, 1, prefix)
 
     if (!experimentalWarned) {
       experimentalWarned = true
@@ -114,8 +115,8 @@ class EventSource extends EventTarget {
       })
     }
 
-    url = webidl.converters.USVString(url)
-    eventSourceInitDict = webidl.converters.EventSourceInitDict(eventSourceInitDict)
+    url = webidl.converters.USVString(url, prefix, 'url')
+    eventSourceInitDict = webidl.converters.EventSourceInitDict(eventSourceInitDict, prefix, 'eventSourceInitDict')
 
     this.#dispatcher = eventSourceInitDict.dispatcher
     this.#state = {
@@ -463,7 +464,7 @@ webidl.converters.EventSourceInitDict = webidl.dictionaryConverter([
   {
     key: 'withCredentials',
     converter: webidl.converters.boolean,
-    defaultValue: false
+    defaultValue: () => false
   },
   {
     key: 'dispatcher', // undici only
diff --git a/lib/web/fetch/formdata.js b/lib/web/fetch/formdata.js
index 029419ffe94..94a84b03ab3 100644
--- a/lib/web/fetch/formdata.js
+++ b/lib/web/fetch/formdata.js
@@ -28,7 +28,8 @@ class FormData {
   append (name, value, filename = undefined) {
     webidl.brandCheck(this, FormData)
 
-    webidl.argumentLengthCheck(arguments, 2, { header: 'FormData.append' })
+    const prefix = 'FormData.append'
+    webidl.argumentLengthCheck(arguments, 2, prefix)
 
     if (arguments.length === 3 && !isBlobLike(value)) {
       throw new TypeError(
@@ -38,12 +39,12 @@ class FormData {
 
     // 1. Let value be value if given; otherwise blobValue.
 
-    name = webidl.converters.USVString(name)
+    name = webidl.converters.USVString(name, prefix, 'name')
     value = isBlobLike(value)
-      ? webidl.converters.Blob(value, { strict: false })
-      : webidl.converters.USVString(value)
+      ? webidl.converters.Blob(value, prefix, 'value', { strict: false })
+      : webidl.converters.USVString(value, prefix, 'value')
     filename = arguments.length === 3
-      ? webidl.converters.USVString(filename)
+      ? webidl.converters.USVString(filename, prefix, 'filename')
       : undefined
 
     // 2. Let entry be the result of creating an entry with
@@ -57,9 +58,10 @@ class FormData {
   delete (name) {
     webidl.brandCheck(this, FormData)
 
-    webidl.argumentLengthCheck(arguments, 1, { header: 'FormData.delete' })
+    const prefix = 'FormData.delete'
+    webidl.argumentLengthCheck(arguments, 1, prefix)
 
-    name = webidl.converters.USVString(name)
+    name = webidl.converters.USVString(name, prefix, 'name')
 
     // The delete(name) method steps are to remove all entries whose name
     // is name from this’s entry list.
@@ -69,9 +71,10 @@ class FormData {
   get (name) {
     webidl.brandCheck(this, FormData)
 
-    webidl.argumentLengthCheck(arguments, 1, { header: 'FormData.get' })
+    const prefix = 'FormData.get'
+    webidl.argumentLengthCheck(arguments, 1, prefix)
 
-    name = webidl.converters.USVString(name)
+    name = webidl.converters.USVString(name, prefix, 'name')
 
     // 1. If there is no entry whose name is name in this’s entry list,
     // then return null.
@@ -88,9 +91,10 @@ class FormData {
   getAll (name) {
     webidl.brandCheck(this, FormData)
 
-    webidl.argumentLengthCheck(arguments, 1, { header: 'FormData.getAll' })
+    const prefix = 'FormData.getAll'
+    webidl.argumentLengthCheck(arguments, 1, prefix)
 
-    name = webidl.converters.USVString(name)
+    name = webidl.converters.USVString(name, prefix, 'name')
 
     // 1. If there is no entry whose name is name in this’s entry list,
     // then return the empty list.
@@ -104,9 +108,10 @@ class FormData {
   has (name) {
     webidl.brandCheck(this, FormData)
 
-    webidl.argumentLengthCheck(arguments, 1, { header: 'FormData.has' })
+    const prefix = 'FormData.has'
+    webidl.argumentLengthCheck(arguments, 1, prefix)
 
-    name = webidl.converters.USVString(name)
+    name = webidl.converters.USVString(name, prefix, 'name')
 
     // The has(name) method steps are to return true if there is an entry
     // whose name is name in this’s entry list; otherwise false.
@@ -116,7 +121,8 @@ class FormData {
   set (name, value, filename = undefined) {
     webidl.brandCheck(this, FormData)
 
-    webidl.argumentLengthCheck(arguments, 2, { header: 'FormData.set' })
+    const prefix = 'FormData.set'
+    webidl.argumentLengthCheck(arguments, 2, prefix)
 
     if (arguments.length === 3 && !isBlobLike(value)) {
       throw new TypeError(
@@ -129,12 +135,12 @@ class FormData {
 
     // 1. Let value be value if given; otherwise blobValue.
 
-    name = webidl.converters.USVString(name)
+    name = webidl.converters.USVString(name, prefix, 'name')
     value = isBlobLike(value)
-      ? webidl.converters.Blob(value, { strict: false })
-      : webidl.converters.USVString(value)
+      ? webidl.converters.Blob(value, prefix, 'name', { strict: false })
+      : webidl.converters.USVString(value, prefix, 'name')
     filename = arguments.length === 3
-      ? webidl.converters.USVString(filename)
+      ? webidl.converters.USVString(filename, prefix, 'name')
       : undefined
 
     // 2. Let entry be the result of creating an entry with name, value, and
diff --git a/lib/web/fetch/headers.js b/lib/web/fetch/headers.js
index 7f2f526a9cb..3157561b470 100644
--- a/lib/web/fetch/headers.js
+++ b/lib/web/fetch/headers.js
@@ -366,7 +366,7 @@ class Headers {
 
     // 2. If init is given, then fill this with init.
     if (init !== undefined) {
-      init = webidl.converters.HeadersInit(init)
+      init = webidl.converters.HeadersInit(init, 'Headers contructor', 'init')
       fill(this, init)
     }
   }
@@ -375,10 +375,11 @@ class Headers {
   append (name, value) {
     webidl.brandCheck(this, Headers)
 
-    webidl.argumentLengthCheck(arguments, 2, { header: 'Headers.append' })
+    webidl.argumentLengthCheck(arguments, 2, 'Headers.append')
 
-    name = webidl.converters.ByteString(name)
-    value = webidl.converters.ByteString(value)
+    const prefix = 'Headers.append'
+    name = webidl.converters.ByteString(name, prefix, 'name')
+    value = webidl.converters.ByteString(value, prefix, 'value')
 
     return appendHeader(this, name, value)
   }
@@ -387,9 +388,10 @@ class Headers {
   delete (name) {
     webidl.brandCheck(this, Headers)
 
-    webidl.argumentLengthCheck(arguments, 1, { header: 'Headers.delete' })
+    webidl.argumentLengthCheck(arguments, 1, 'Headers.delete')
 
-    name = webidl.converters.ByteString(name)
+    const prefix = 'Headers.delete'
+    name = webidl.converters.ByteString(name, prefix, 'name')
 
     // 1. If name is not a header name, then throw a TypeError.
     if (!isValidHeaderName(name)) {
@@ -432,14 +434,15 @@ class Headers {
   get (name) {
     webidl.brandCheck(this, Headers)
 
-    webidl.argumentLengthCheck(arguments, 1, { header: 'Headers.get' })
+    webidl.argumentLengthCheck(arguments, 1, 'Headers.get')
 
-    name = webidl.converters.ByteString(name)
+    const prefix = 'Headers.get'
+    name = webidl.converters.ByteString(name, prefix, 'name')
 
     // 1. If name is not a header name, then throw a TypeError.
     if (!isValidHeaderName(name)) {
       throw webidl.errors.invalidArgument({
-        prefix: 'Headers.get',
+        prefix,
         value: name,
         type: 'header name'
       })
@@ -454,14 +457,15 @@ class Headers {
   has (name) {
     webidl.brandCheck(this, Headers)
 
-    webidl.argumentLengthCheck(arguments, 1, { header: 'Headers.has' })
+    webidl.argumentLengthCheck(arguments, 1, 'Headers.has')
 
-    name = webidl.converters.ByteString(name)
+    const prefix = 'Headers.has'
+    name = webidl.converters.ByteString(name, prefix, 'name')
 
     // 1. If name is not a header name, then throw a TypeError.
     if (!isValidHeaderName(name)) {
       throw webidl.errors.invalidArgument({
-        prefix: 'Headers.has',
+        prefix,
         value: name,
         type: 'header name'
       })
@@ -476,10 +480,11 @@ class Headers {
   set (name, value) {
     webidl.brandCheck(this, Headers)
 
-    webidl.argumentLengthCheck(arguments, 2, { header: 'Headers.set' })
+    webidl.argumentLengthCheck(arguments, 2, 'Headers.set')
 
-    name = webidl.converters.ByteString(name)
-    value = webidl.converters.ByteString(value)
+    const prefix = 'Headers.set'
+    name = webidl.converters.ByteString(name, prefix, 'name')
+    value = webidl.converters.ByteString(value, prefix, 'value')
 
     // 1. Normalize value.
     value = headerValueNormalize(value)
@@ -488,13 +493,13 @@ class Headers {
     //    header value, then throw a TypeError.
     if (!isValidHeaderName(name)) {
       throw webidl.errors.invalidArgument({
-        prefix: 'Headers.set',
+        prefix,
         value: name,
         type: 'header name'
       })
     } else if (!isValidHeaderValue(value)) {
       throw webidl.errors.invalidArgument({
-        prefix: 'Headers.set',
+        prefix,
         value,
         type: 'header value'
       })
@@ -616,7 +621,7 @@ Object.defineProperties(Headers.prototype, {
   }
 })
 
-webidl.converters.HeadersInit = function (V) {
+webidl.converters.HeadersInit = function (V, prefix, argument) {
   if (webidl.util.Type(V) === 'Object') {
     const iterator = Reflect.get(V, Symbol.iterator)
 
@@ -627,10 +632,10 @@ webidl.converters.HeadersInit = function (V) {
     }
 
     if (typeof iterator === 'function') {
-      return webidl.converters['sequence<sequence<ByteString>>'](V, iterator.bind(V))
+      return webidl.converters['sequence<sequence<ByteString>>'](V, prefix, argument, iterator.bind(V))
     }
 
-    return webidl.converters['record<ByteString, ByteString>'](V)
+    return webidl.converters['record<ByteString, ByteString>'](V, prefix, argument)
   }
 
   throw webidl.errors.conversionFailed({
diff --git a/lib/web/fetch/index.js b/lib/web/fetch/index.js
index a082797e575..82ccb26865c 100644
--- a/lib/web/fetch/index.js
+++ b/lib/web/fetch/index.js
@@ -122,7 +122,7 @@ class Fetch extends EE {
 
 // https://fetch.spec.whatwg.org/#fetch-method
 function fetch (input, init = undefined) {
-  webidl.argumentLengthCheck(arguments, 1, { header: 'globalThis.fetch' })
+  webidl.argumentLengthCheck(arguments, 1, 'globalThis.fetch')
 
   // 1. Let p be a new promise.
   const p = createDeferredPromise()
diff --git a/lib/web/fetch/request.js b/lib/web/fetch/request.js
index d963986ce2d..1441a58b06e 100644
--- a/lib/web/fetch/request.js
+++ b/lib/web/fetch/request.js
@@ -88,10 +88,11 @@ class Request {
       return
     }
 
-    webidl.argumentLengthCheck(arguments, 1, { header: 'Request constructor' })
+    const prefix = 'Request constructor'
+    webidl.argumentLengthCheck(arguments, 1, prefix)
 
-    input = webidl.converters.RequestInfo(input)
-    init = webidl.converters.RequestInit(init)
+    input = webidl.converters.RequestInfo(input, prefix, 'input')
+    init = webidl.converters.RequestInit(init, prefix, 'init')
 
     // 1. Let request be null.
     let request = null
@@ -932,16 +933,16 @@ webidl.converters.Request = webidl.interfaceConverter(
 )
 
 // https://fetch.spec.whatwg.org/#requestinfo
-webidl.converters.RequestInfo = function (V) {
+webidl.converters.RequestInfo = function (V, prefix, argument) {
   if (typeof V === 'string') {
-    return webidl.converters.USVString(V)
+    return webidl.converters.USVString(V, prefix, argument)
   }
 
   if (V instanceof Request) {
-    return webidl.converters.Request(V)
+    return webidl.converters.Request(V, prefix, argument)
   }
 
-  return webidl.converters.USVString(V)
+  return webidl.converters.USVString(V, prefix, argument)
 }
 
 webidl.converters.AbortSignal = webidl.interfaceConverter(
@@ -1011,6 +1012,8 @@ webidl.converters.RequestInit = webidl.dictionaryConverter([
     converter: webidl.nullableConverter(
       (signal) => webidl.converters.AbortSignal(
         signal,
+        'RequestInit',
+        'signal',
         { strict: false }
       )
     )
diff --git a/lib/web/fetch/response.js b/lib/web/fetch/response.js
index f609e3d4c5d..222a9a5b2f7 100644
--- a/lib/web/fetch/response.js
+++ b/lib/web/fetch/response.js
@@ -43,7 +43,7 @@ class Response {
 
   // https://fetch.spec.whatwg.org/#dom-response-json
   static json (data, init = {}) {
-    webidl.argumentLengthCheck(arguments, 1, { header: 'Response.json' })
+    webidl.argumentLengthCheck(arguments, 1, 'Response.json')
 
     if (init !== null) {
       init = webidl.converters.ResponseInit(init)
@@ -70,7 +70,7 @@ class Response {
 
   // Creates a redirect Response that redirects to url with status status.
   static redirect (url, status = 302) {
-    webidl.argumentLengthCheck(arguments, 1, { header: 'Response.redirect' })
+    webidl.argumentLengthCheck(arguments, 1, 'Response.redirect')
 
     url = webidl.converters.USVString(url)
     status = webidl.converters['unsigned short'](status)
@@ -526,34 +526,34 @@ webidl.converters.URLSearchParams = webidl.interfaceConverter(
 )
 
 // https://fetch.spec.whatwg.org/#typedefdef-xmlhttprequestbodyinit
-webidl.converters.XMLHttpRequestBodyInit = function (V) {
+webidl.converters.XMLHttpRequestBodyInit = function (V, prefix, name) {
   if (typeof V === 'string') {
-    return webidl.converters.USVString(V)
+    return webidl.converters.USVString(V, prefix, name)
   }
 
   if (isBlobLike(V)) {
-    return webidl.converters.Blob(V, { strict: false })
+    return webidl.converters.Blob(V, prefix, name, { strict: false })
   }
 
   if (ArrayBuffer.isView(V) || types.isArrayBuffer(V)) {
-    return webidl.converters.BufferSource(V)
+    return webidl.converters.BufferSource(V, prefix, name)
   }
 
   if (util.isFormDataLike(V)) {
-    return webidl.converters.FormData(V, { strict: false })
+    return webidl.converters.FormData(V, prefix, name, { strict: false })
   }
 
   if (V instanceof URLSearchParams) {
-    return webidl.converters.URLSearchParams(V)
+    return webidl.converters.URLSearchParams(V, prefix, name)
   }
 
-  return webidl.converters.DOMString(V)
+  return webidl.converters.DOMString(V, prefix, name)
 }
 
 // https://fetch.spec.whatwg.org/#bodyinit
-webidl.converters.BodyInit = function (V) {
+webidl.converters.BodyInit = function (V, prefix, argument) {
   if (V instanceof ReadableStream) {
-    return webidl.converters.ReadableStream(V)
+    return webidl.converters.ReadableStream(V, prefix, argument)
   }
 
   // Note: the spec doesn't include async iterables,
@@ -562,19 +562,19 @@ webidl.converters.BodyInit = function (V) {
     return V
   }
 
-  return webidl.converters.XMLHttpRequestBodyInit(V)
+  return webidl.converters.XMLHttpRequestBodyInit(V, prefix, argument)
 }
 
 webidl.converters.ResponseInit = webidl.dictionaryConverter([
   {
     key: 'status',
     converter: webidl.converters['unsigned short'],
-    defaultValue: 200
+    defaultValue: () => 200
   },
   {
     key: 'statusText',
     converter: webidl.converters.ByteString,
-    defaultValue: ''
+    defaultValue: () => ''
   },
   {
     key: 'headers',
diff --git a/lib/web/fetch/util.js b/lib/web/fetch/util.js
index a684c27d883..299f4e64c81 100644
--- a/lib/web/fetch/util.js
+++ b/lib/web/fetch/util.js
@@ -1016,7 +1016,7 @@ function iteratorMixin (name, object, kInternalIterator, keyIndex = 0, valueInde
       configurable: true,
       value: function forEach (callbackfn, thisArg = globalThis) {
         webidl.brandCheck(this, object)
-        webidl.argumentLengthCheck(arguments, 1, { header: `${name}.forEach` })
+        webidl.argumentLengthCheck(arguments, 1, `${name}.forEach`)
         if (typeof callbackfn !== 'function') {
           throw new TypeError(
             `Failed to execute 'forEach' on '${name}': parameter 1 is not of type 'Function'.`
diff --git a/lib/web/fetch/webidl.js b/lib/web/fetch/webidl.js
index ceb7f3e8b09..c90e411afca 100644
--- a/lib/web/fetch/webidl.js
+++ b/lib/web/fetch/webidl.js
@@ -33,14 +33,18 @@ webidl.errors.invalidArgument = function (context) {
 }
 
 // https://webidl.spec.whatwg.org/#implements
-webidl.brandCheck = function (V, I, opts = undefined) {
+webidl.brandCheck = function (V, I, opts) {
   if (opts?.strict !== false) {
     if (!(V instanceof I)) {
-      throw new TypeError('Illegal invocation')
+      const err = new TypeError('Illegal invocation')
+      err.code = 'ERR_INVALID_THIS' // node compat.
+      throw err
     }
   } else {
     if (V?.[Symbol.toStringTag] !== I.prototype[Symbol.toStringTag]) {
-      throw new TypeError('Illegal invocation')
+      const err = new TypeError('Illegal invocation')
+      err.code = 'ERR_INVALID_THIS' // node compat.
+      throw err
     }
   }
 }
@@ -50,7 +54,7 @@ webidl.argumentLengthCheck = function ({ length }, min, ctx) {
     throw webidl.errors.exception({
       message: `${min} argument${min !== 1 ? 's' : ''} required, ` +
                `but${length ? ' only' : ''} ${length} found.`,
-      ...ctx
+      header: ctx
     })
   }
 }
@@ -83,7 +87,7 @@ webidl.util.Type = function (V) {
 }
 
 // https://webidl.spec.whatwg.org/#abstract-opdef-converttoint
-webidl.util.ConvertToInt = function (V, bitLength, signedness, opts = {}) {
+webidl.util.ConvertToInt = function (V, bitLength, signedness, opts) {
   let upperBound
   let lowerBound
 
@@ -127,7 +131,7 @@ webidl.util.ConvertToInt = function (V, bitLength, signedness, opts = {}) {
 
   // 6. If the conversion is to an IDL type associated
   //    with the [EnforceRange] extended attribute, then:
-  if (opts.enforceRange === true) {
+  if (opts?.enforceRange === true) {
     // 1. If x is NaN, +∞, or −∞, then throw a TypeError.
     if (
       Number.isNaN(x) ||
@@ -159,7 +163,7 @@ webidl.util.ConvertToInt = function (V, bitLength, signedness, opts = {}) {
   // 7. If x is not NaN and the conversion is to an IDL
   //    type associated with the [Clamp] extended
   //    attribute, then:
-  if (!Number.isNaN(x) && opts.clamp === true) {
+  if (!Number.isNaN(x) && opts?.clamp === true) {
     // 1. Set x to min(max(x, lowerBound), upperBound).
     x = Math.min(Math.max(x, lowerBound), upperBound)
 
@@ -233,12 +237,12 @@ webidl.util.Stringify = function (V) {
 
 // https://webidl.spec.whatwg.org/#es-sequence
 webidl.sequenceConverter = function (converter) {
-  return (V, Iterable) => {
+  return (V, prefix, argument, Iterable) => {
     // 1. If Type(V) is not Object, throw a TypeError.
     if (webidl.util.Type(V) !== 'Object') {
       throw webidl.errors.exception({
-        header: 'Sequence',
-        message: `Value of type ${webidl.util.Type(V)} is not an Object.`
+        header: prefix,
+        message: `${argument} (${webidl.util.Stringify(V)}) is not an Object.`
       })
     }
 
@@ -253,8 +257,8 @@ webidl.sequenceConverter = function (converter) {
       typeof method.next !== 'function'
     ) {
       throw webidl.errors.exception({
-        header: 'Sequence',
-        message: 'Object is not an iterator.'
+        header: prefix,
+        message: `${argument} is not iterable.`
       })
     }
 
@@ -266,7 +270,7 @@ webidl.sequenceConverter = function (converter) {
         break
       }
 
-      seq.push(converter(value))
+      seq.push(converter(value, prefix, argument))
     }
 
     return seq
@@ -275,12 +279,12 @@ webidl.sequenceConverter = function (converter) {
 
 // https://webidl.spec.whatwg.org/#es-to-record
 webidl.recordConverter = function (keyConverter, valueConverter) {
-  return (O) => {
+  return (O, prefix, argument) => {
     // 1. If Type(O) is not Object, throw a TypeError.
     if (webidl.util.Type(O) !== 'Object') {
       throw webidl.errors.exception({
-        header: 'Record',
-        message: `Value of type ${webidl.util.Type(O)} is not an Object.`
+        header: prefix,
+        message: `${argument} ("${webidl.util.Type(O)}") is not an Object.`
       })
     }
 
@@ -293,11 +297,11 @@ webidl.recordConverter = function (keyConverter, valueConverter) {
 
       for (const key of keys) {
         // 1. Let typedKey be key converted to an IDL value of type K.
-        const typedKey = keyConverter(key)
+        const typedKey = keyConverter(key, prefix, argument)
 
         // 2. Let value be ? Get(O, key).
         // 3. Let typedValue be value converted to an IDL value of type V.
-        const typedValue = valueConverter(O[key])
+        const typedValue = valueConverter(O[key], prefix, argument)
 
         // 4. Set result[typedKey] to typedValue.
         result[typedKey] = typedValue
@@ -318,11 +322,11 @@ webidl.recordConverter = function (keyConverter, valueConverter) {
       // 2. If desc is not undefined and desc.[[Enumerable]] is true:
       if (desc?.enumerable) {
         // 1. Let typedKey be key converted to an IDL value of type K.
-        const typedKey = keyConverter(key)
+        const typedKey = keyConverter(key, prefix, argument)
 
         // 2. Let value be ? Get(O, key).
         // 3. Let typedValue be value converted to an IDL value of type V.
-        const typedValue = valueConverter(O[key])
+        const typedValue = valueConverter(O[key], prefix, argument)
 
         // 4. Set result[typedKey] to typedValue.
         result[typedKey] = typedValue
@@ -335,11 +339,11 @@ webidl.recordConverter = function (keyConverter, valueConverter) {
 }
 
 webidl.interfaceConverter = function (i) {
-  return (V, opts = {}) => {
-    if (opts.strict !== false && !(V instanceof i)) {
+  return (V, prefix, argument, opts) => {
+    if (opts?.strict !== false && !(V instanceof i)) {
       throw webidl.errors.exception({
-        header: i.name,
-        message: `Expected ${webidl.util.Stringify(V)} to be an instance of ${i.name}.`
+        header: prefix,
+        message: `Expected ${argument} ("${webidl.util.Stringify(V)}") to be an instance of ${i.name}.`
       })
     }
 
@@ -348,7 +352,7 @@ webidl.interfaceConverter = function (i) {
 }
 
 webidl.dictionaryConverter = function (converters) {
-  return (dictionary) => {
+  return (dictionary, prefix, argument) => {
     const type = webidl.util.Type(dictionary)
     const dict = {}
 
@@ -356,7 +360,7 @@ webidl.dictionaryConverter = function (converters) {
       return dict
     } else if (type !== 'Object') {
       throw webidl.errors.exception({
-        header: 'Dictionary',
+        header: prefix,
         message: `Expected ${dictionary} to be one of: Null, Undefined, Object.`
       })
     }
@@ -367,7 +371,7 @@ webidl.dictionaryConverter = function (converters) {
       if (required === true) {
         if (!Object.hasOwn(dictionary, key)) {
           throw webidl.errors.exception({
-            header: 'Dictionary',
+            header: prefix,
             message: `Missing required key "${key}".`
           })
         }
@@ -379,21 +383,21 @@ webidl.dictionaryConverter = function (converters) {
       // Only use defaultValue if value is undefined and
       // a defaultValue options was provided.
       if (hasDefault && value !== null) {
-        value = value ?? defaultValue
+        value ??= defaultValue()
       }
 
       // A key can be optional and have no default value.
       // When this happens, do not perform a conversion,
       // and do not assign the key a value.
       if (required || hasDefault || value !== undefined) {
-        value = converter(value)
+        value = converter(value, prefix, argument)
 
         if (
           options.allowedValues &&
           !options.allowedValues.includes(value)
         ) {
           throw webidl.errors.exception({
-            header: 'Dictionary',
+            header: prefix,
             message: `${value} is not an accepted type. Expected one of ${options.allowedValues.join(', ')}.`
           })
         }
@@ -407,28 +411,31 @@ webidl.dictionaryConverter = function (converters) {
 }
 
 webidl.nullableConverter = function (converter) {
-  return (V) => {
+  return (V, prefix, argument) => {
     if (V === null) {
       return V
     }
 
-    return converter(V)
+    return converter(V, prefix, argument)
   }
 }
 
 // https://webidl.spec.whatwg.org/#es-DOMString
-webidl.converters.DOMString = function (V, opts = {}) {
+webidl.converters.DOMString = function (V, prefix, argument, opts) {
   // 1. If V is null and the conversion is to an IDL type
   //    associated with the [LegacyNullToEmptyString]
   //    extended attribute, then return the DOMString value
   //    that represents the empty string.
-  if (V === null && opts.legacyNullToEmptyString) {
+  if (V === null && opts?.legacyNullToEmptyString) {
     return ''
   }
 
   // 2. Let x be ? ToString(V).
   if (typeof V === 'symbol') {
-    throw new TypeError('Could not convert argument of type symbol to string.')
+    throw webidl.errors.exception({
+      header: prefix,
+      message: `${argument} is a symbol, which cannot be converted to a DOMString.`
+    })
   }
 
   // 3. Return the IDL DOMString value that represents the
@@ -438,10 +445,10 @@ webidl.converters.DOMString = function (V, opts = {}) {
 }
 
 // https://webidl.spec.whatwg.org/#es-ByteString
-webidl.converters.ByteString = function (V) {
+webidl.converters.ByteString = function (V, prefix, argument) {
   // 1. Let x be ? ToString(V).
   // Note: DOMString converter perform ? ToString(V)
-  const x = webidl.converters.DOMString(V)
+  const x = webidl.converters.DOMString(V, prefix, argument)
 
   // 2. If the value of any element of x is greater than
   //    255, then throw a TypeError.
@@ -461,6 +468,7 @@ webidl.converters.ByteString = function (V) {
 }
 
 // https://webidl.spec.whatwg.org/#es-USVString
+// TODO: rewrite this so we can control the errors thrown
 webidl.converters.USVString = toUSVString
 
 // https://webidl.spec.whatwg.org/#es-boolean
@@ -479,9 +487,9 @@ webidl.converters.any = function (V) {
 }
 
 // https://webidl.spec.whatwg.org/#es-long-long
-webidl.converters['long long'] = function (V) {
+webidl.converters['long long'] = function (V, prefix, argument) {
   // 1. Let x be ? ConvertToInt(V, 64, "signed").
-  const x = webidl.util.ConvertToInt(V, 64, 'signed')
+  const x = webidl.util.ConvertToInt(V, 64, 'signed', undefined, prefix, argument)
 
   // 2. Return the IDL long long value that represents
   //    the same numeric value as x.
@@ -489,9 +497,9 @@ webidl.converters['long long'] = function (V) {
 }
 
 // https://webidl.spec.whatwg.org/#es-unsigned-long-long
-webidl.converters['unsigned long long'] = function (V) {
+webidl.converters['unsigned long long'] = function (V, prefix, argument) {
   // 1. Let x be ? ConvertToInt(V, 64, "unsigned").
-  const x = webidl.util.ConvertToInt(V, 64, 'unsigned')
+  const x = webidl.util.ConvertToInt(V, 64, 'unsigned', undefined, prefix, argument)
 
   // 2. Return the IDL unsigned long long value that
   //    represents the same numeric value as x.
@@ -499,9 +507,9 @@ webidl.converters['unsigned long long'] = function (V) {
 }
 
 // https://webidl.spec.whatwg.org/#es-unsigned-long
-webidl.converters['unsigned long'] = function (V) {
+webidl.converters['unsigned long'] = function (V, prefix, argument) {
   // 1. Let x be ? ConvertToInt(V, 32, "unsigned").
-  const x = webidl.util.ConvertToInt(V, 32, 'unsigned')
+  const x = webidl.util.ConvertToInt(V, 32, 'unsigned', undefined, prefix, argument)
 
   // 2. Return the IDL unsigned long value that
   //    represents the same numeric value as x.
@@ -509,9 +517,9 @@ webidl.converters['unsigned long'] = function (V) {
 }
 
 // https://webidl.spec.whatwg.org/#es-unsigned-short
-webidl.converters['unsigned short'] = function (V, opts) {
+webidl.converters['unsigned short'] = function (V, prefix, argument, opts) {
   // 1. Let x be ? ConvertToInt(V, 16, "unsigned").
-  const x = webidl.util.ConvertToInt(V, 16, 'unsigned', opts)
+  const x = webidl.util.ConvertToInt(V, 16, 'unsigned', opts, prefix, argument)
 
   // 2. Return the IDL unsigned short value that represents
   //    the same numeric value as x.
@@ -519,7 +527,7 @@ webidl.converters['unsigned short'] = function (V, opts) {
 }
 
 // https://webidl.spec.whatwg.org/#idl-ArrayBuffer
-webidl.converters.ArrayBuffer = function (V, opts = {}) {
+webidl.converters.ArrayBuffer = function (V, prefix, argument, opts) {
   // 1. If Type(V) is not Object, or V does not have an
   //    [[ArrayBufferData]] internal slot, then throw a
   //    TypeError.
@@ -530,8 +538,8 @@ webidl.converters.ArrayBuffer = function (V, opts = {}) {
     !types.isAnyArrayBuffer(V)
   ) {
     throw webidl.errors.conversionFailed({
-      prefix: webidl.util.Stringify(V),
-      argument: webidl.util.Stringify(V),
+      prefix,
+      argument: `${argument} ("${webidl.util.Stringify(V)}")`,
       types: ['ArrayBuffer']
     })
   }
@@ -540,7 +548,7 @@ webidl.converters.ArrayBuffer = function (V, opts = {}) {
   //    with the [AllowShared] extended attribute, and
   //    IsSharedArrayBuffer(V) is true, then throw a
   //    TypeError.
-  if (opts.allowShared === false && types.isSharedArrayBuffer(V)) {
+  if (opts?.allowShared === false && types.isSharedArrayBuffer(V)) {
     throw webidl.errors.exception({
       header: 'ArrayBuffer',
       message: 'SharedArrayBuffer is not allowed.'
@@ -563,7 +571,7 @@ webidl.converters.ArrayBuffer = function (V, opts = {}) {
   return V
 }
 
-webidl.converters.TypedArray = function (V, T, opts = {}) {
+webidl.converters.TypedArray = function (V, T, prefix, name, opts) {
   // 1. Let T be the IDL type V is being converted to.
 
   // 2. If Type(V) is not Object, or V does not have a
@@ -575,8 +583,8 @@ webidl.converters.TypedArray = function (V, T, opts = {}) {
     V.constructor.name !== T.name
   ) {
     throw webidl.errors.conversionFailed({
-      prefix: `${T.name}`,
-      argument: webidl.util.Stringify(V),
+      prefix,
+      argument: `${name} ("${webidl.util.Stringify(V)}")`,
       types: [T.name]
     })
   }
@@ -585,7 +593,7 @@ webidl.converters.TypedArray = function (V, T, opts = {}) {
   //    with the [AllowShared] extended attribute, and
   //    IsSharedArrayBuffer(V.[[ViewedArrayBuffer]]) is
   //    true, then throw a TypeError.
-  if (opts.allowShared === false && types.isSharedArrayBuffer(V.buffer)) {
+  if (opts?.allowShared === false && types.isSharedArrayBuffer(V.buffer)) {
     throw webidl.errors.exception({
       header: 'ArrayBuffer',
       message: 'SharedArrayBuffer is not allowed.'
@@ -608,13 +616,13 @@ webidl.converters.TypedArray = function (V, T, opts = {}) {
   return V
 }
 
-webidl.converters.DataView = function (V, opts = {}) {
+webidl.converters.DataView = function (V, prefix, name, opts) {
   // 1. If Type(V) is not Object, or V does not have a
   //    [[DataView]] internal slot, then throw a TypeError.
   if (webidl.util.Type(V) !== 'Object' || !types.isDataView(V)) {
     throw webidl.errors.exception({
-      header: 'DataView',
-      message: 'Object is not a DataView.'
+      header: prefix,
+      message: `${name} is not a DataView.`
     })
   }
 
@@ -622,7 +630,7 @@ webidl.converters.DataView = function (V, opts = {}) {
   //    with the [AllowShared] extended attribute, and
   //    IsSharedArrayBuffer(V.[[ViewedArrayBuffer]]) is true,
   //    then throw a TypeError.
-  if (opts.allowShared === false && types.isSharedArrayBuffer(V.buffer)) {
+  if (opts?.allowShared === false && types.isSharedArrayBuffer(V.buffer)) {
     throw webidl.errors.exception({
       header: 'ArrayBuffer',
       message: 'SharedArrayBuffer is not allowed.'
@@ -646,20 +654,24 @@ webidl.converters.DataView = function (V, opts = {}) {
 }
 
 // https://webidl.spec.whatwg.org/#BufferSource
-webidl.converters.BufferSource = function (V, opts = {}) {
+webidl.converters.BufferSource = function (V, prefix, name, opts) {
   if (types.isAnyArrayBuffer(V)) {
-    return webidl.converters.ArrayBuffer(V, { ...opts, allowShared: false })
+    return webidl.converters.ArrayBuffer(V, prefix, name, { ...opts, allowShared: false })
   }
 
   if (types.isTypedArray(V)) {
-    return webidl.converters.TypedArray(V, V.constructor, { ...opts, allowShared: false })
+    return webidl.converters.TypedArray(V, V.constructor, prefix, name, { ...opts, allowShared: false })
   }
 
   if (types.isDataView(V)) {
-    return webidl.converters.DataView(V, opts, { ...opts, allowShared: false })
+    return webidl.converters.DataView(V, prefix, name, { ...opts, allowShared: false })
   }
 
-  throw new TypeError(`Could not convert ${webidl.util.Stringify(V)} to a BufferSource.`)
+  throw webidl.errors.conversionFailed({
+    prefix,
+    argument: `${name} ("${webidl.util.Stringify(V)}")`,
+    types: ['BufferSource']
+  })
 }
 
 webidl.converters['sequence<ByteString>'] = webidl.sequenceConverter(
diff --git a/lib/web/fileapi/filereader.js b/lib/web/fileapi/filereader.js
index 0cca813994e..ccebe692a6f 100644
--- a/lib/web/fileapi/filereader.js
+++ b/lib/web/fileapi/filereader.js
@@ -39,7 +39,7 @@ class FileReader extends EventTarget {
   readAsArrayBuffer (blob) {
     webidl.brandCheck(this, FileReader)
 
-    webidl.argumentLengthCheck(arguments, 1, { header: 'FileReader.readAsArrayBuffer' })
+    webidl.argumentLengthCheck(arguments, 1, 'FileReader.readAsArrayBuffer')
 
     blob = webidl.converters.Blob(blob, { strict: false })
 
@@ -55,7 +55,7 @@ class FileReader extends EventTarget {
   readAsBinaryString (blob) {
     webidl.brandCheck(this, FileReader)
 
-    webidl.argumentLengthCheck(arguments, 1, { header: 'FileReader.readAsBinaryString' })
+    webidl.argumentLengthCheck(arguments, 1, 'FileReader.readAsBinaryString')
 
     blob = webidl.converters.Blob(blob, { strict: false })
 
@@ -72,12 +72,12 @@ class FileReader extends EventTarget {
   readAsText (blob, encoding = undefined) {
     webidl.brandCheck(this, FileReader)
 
-    webidl.argumentLengthCheck(arguments, 1, { header: 'FileReader.readAsText' })
+    webidl.argumentLengthCheck(arguments, 1, 'FileReader.readAsText')
 
     blob = webidl.converters.Blob(blob, { strict: false })
 
     if (encoding !== undefined) {
-      encoding = webidl.converters.DOMString(encoding)
+      encoding = webidl.converters.DOMString(encoding, 'FileReader.readAsText', 'encoding')
     }
 
     // The readAsText(blob, encoding) method, when invoked,
@@ -92,7 +92,7 @@ class FileReader extends EventTarget {
   readAsDataURL (blob) {
     webidl.brandCheck(this, FileReader)
 
-    webidl.argumentLengthCheck(arguments, 1, { header: 'FileReader.readAsDataURL' })
+    webidl.argumentLengthCheck(arguments, 1, 'FileReader.readAsDataURL')
 
     blob = webidl.converters.Blob(blob, { strict: false })
 
diff --git a/lib/web/fileapi/progressevent.js b/lib/web/fileapi/progressevent.js
index 778cf224c6a..2d09d18107d 100644
--- a/lib/web/fileapi/progressevent.js
+++ b/lib/web/fileapi/progressevent.js
@@ -9,7 +9,7 @@ const kState = Symbol('ProgressEvent state')
  */
 class ProgressEvent extends Event {
   constructor (type, eventInitDict = {}) {
-    type = webidl.converters.DOMString(type)
+    type = webidl.converters.DOMString(type, 'ProgressEvent constructor', 'type')
     eventInitDict = webidl.converters.ProgressEventInit(eventInitDict ?? {})
 
     super(type, eventInitDict)
@@ -44,32 +44,32 @@ webidl.converters.ProgressEventInit = webidl.dictionaryConverter([
   {
     key: 'lengthComputable',
     converter: webidl.converters.boolean,
-    defaultValue: false
+    defaultValue: () => false
   },
   {
     key: 'loaded',
     converter: webidl.converters['unsigned long long'],
-    defaultValue: 0
+    defaultValue: () => 0
   },
   {
     key: 'total',
     converter: webidl.converters['unsigned long long'],
-    defaultValue: 0
+    defaultValue: () => 0
   },
   {
     key: 'bubbles',
     converter: webidl.converters.boolean,
-    defaultValue: false
+    defaultValue: () => false
   },
   {
     key: 'cancelable',
     converter: webidl.converters.boolean,
-    defaultValue: false
+    defaultValue: () => false
   },
   {
     key: 'composed',
     converter: webidl.converters.boolean,
-    defaultValue: false
+    defaultValue: () => false
   }
 ])
 
diff --git a/lib/web/websocket/events.js b/lib/web/websocket/events.js
index 7b3bb263c61..760b7297359 100644
--- a/lib/web/websocket/events.js
+++ b/lib/web/websocket/events.js
@@ -17,10 +17,11 @@ class MessageEvent extends Event {
       return
     }
 
-    webidl.argumentLengthCheck(arguments, 1, { header: 'MessageEvent constructor' })
+    const prefix = 'MessageEvent constructor'
+    webidl.argumentLengthCheck(arguments, 1, prefix)
 
-    type = webidl.converters.DOMString(type)
-    eventInitDict = webidl.converters.MessageEventInit(eventInitDict)
+    type = webidl.converters.DOMString(type, prefix, 'type')
+    eventInitDict = webidl.converters.MessageEventInit(eventInitDict, prefix, 'eventInitDict')
 
     super(type, eventInitDict)
 
@@ -73,7 +74,7 @@ class MessageEvent extends Event {
   ) {
     webidl.brandCheck(this, MessageEvent)
 
-    webidl.argumentLengthCheck(arguments, 1, { header: 'MessageEvent.initMessageEvent' })
+    webidl.argumentLengthCheck(arguments, 1, 'MessageEvent.initMessageEvent')
 
     return new MessageEvent(type, {
       bubbles, cancelable, data, origin, lastEventId, source, ports
@@ -102,9 +103,10 @@ class CloseEvent extends Event {
   #eventInit
 
   constructor (type, eventInitDict = {}) {
-    webidl.argumentLengthCheck(arguments, 1, { header: 'CloseEvent constructor' })
+    const prefix = 'CloseEvent constructor'
+    webidl.argumentLengthCheck(arguments, 1, prefix)
 
-    type = webidl.converters.DOMString(type)
+    type = webidl.converters.DOMString(type, prefix, 'type')
     eventInitDict = webidl.converters.CloseEventInit(eventInitDict)
 
     super(type, eventInitDict)
@@ -136,11 +138,12 @@ class ErrorEvent extends Event {
   #eventInit
 
   constructor (type, eventInitDict) {
-    webidl.argumentLengthCheck(arguments, 1, { header: 'ErrorEvent constructor' })
+    const prefix = 'ErrorEvent constructor'
+    webidl.argumentLengthCheck(arguments, 1, prefix)
 
     super(type, eventInitDict)
 
-    type = webidl.converters.DOMString(type)
+    type = webidl.converters.DOMString(type, prefix, 'type')
     eventInitDict = webidl.converters.ErrorEventInit(eventInitDict ?? {})
 
     this.#eventInit = eventInitDict
@@ -222,17 +225,17 @@ const eventInit = [
   {
     key: 'bubbles',
     converter: webidl.converters.boolean,
-    defaultValue: false
+    defaultValue: () => false
   },
   {
     key: 'cancelable',
     converter: webidl.converters.boolean,
-    defaultValue: false
+    defaultValue: () => false
   },
   {
     key: 'composed',
     converter: webidl.converters.boolean,
-    defaultValue: false
+    defaultValue: () => false
   }
 ]
 
@@ -241,31 +244,29 @@ webidl.converters.MessageEventInit = webidl.dictionaryConverter([
   {
     key: 'data',
     converter: webidl.converters.any,
-    defaultValue: null
+    defaultValue: () => null
   },
   {
     key: 'origin',
     converter: webidl.converters.USVString,
-    defaultValue: ''
+    defaultValue: () => ''
   },
   {
     key: 'lastEventId',
     converter: webidl.converters.DOMString,
-    defaultValue: ''
+    defaultValue: () => ''
   },
   {
     key: 'source',
     // Node doesn't implement WindowProxy or ServiceWorker, so the only
     // valid value for source is a MessagePort.
     converter: webidl.nullableConverter(webidl.converters.MessagePort),
-    defaultValue: null
+    defaultValue: () => null
   },
   {
     key: 'ports',
     converter: webidl.converters['sequence<MessagePort>'],
-    get defaultValue () {
-      return []
-    }
+    defaultValue: () => new Array(0)
   }
 ])
 
@@ -274,17 +275,17 @@ webidl.converters.CloseEventInit = webidl.dictionaryConverter([
   {
     key: 'wasClean',
     converter: webidl.converters.boolean,
-    defaultValue: false
+    defaultValue: () => false
   },
   {
     key: 'code',
     converter: webidl.converters['unsigned short'],
-    defaultValue: 0
+    defaultValue: () => 0
   },
   {
     key: 'reason',
     converter: webidl.converters.USVString,
-    defaultValue: ''
+    defaultValue: () => ''
   }
 ])
 
@@ -293,22 +294,22 @@ webidl.converters.ErrorEventInit = webidl.dictionaryConverter([
   {
     key: 'message',
     converter: webidl.converters.DOMString,
-    defaultValue: ''
+    defaultValue: () => ''
   },
   {
     key: 'filename',
     converter: webidl.converters.USVString,
-    defaultValue: ''
+    defaultValue: () => ''
   },
   {
     key: 'lineno',
     converter: webidl.converters['unsigned long'],
-    defaultValue: 0
+    defaultValue: () => 0
   },
   {
     key: 'colno',
     converter: webidl.converters['unsigned long'],
-    defaultValue: 0
+    defaultValue: () => 0
   },
   {
     key: 'error',
diff --git a/lib/web/websocket/websocket.js b/lib/web/websocket/websocket.js
index c4b40b43188..00e81cbafca 100644
--- a/lib/web/websocket/websocket.js
+++ b/lib/web/websocket/websocket.js
@@ -51,7 +51,8 @@ class WebSocket extends EventTarget {
   constructor (url, protocols = []) {
     super()
 
-    webidl.argumentLengthCheck(arguments, 1, { header: 'WebSocket constructor' })
+    const prefix = 'WebSocket constructor'
+    webidl.argumentLengthCheck(arguments, 1, prefix)
 
     if (!experimentalWarned) {
       experimentalWarned = true
@@ -60,9 +61,9 @@ class WebSocket extends EventTarget {
       })
     }
 
-    const options = webidl.converters['DOMString or sequence<DOMString> or WebSocketInit'](protocols)
+    const options = webidl.converters['DOMString or sequence<DOMString> or WebSocketInit'](protocols, prefix, 'options')
 
-    url = webidl.converters.USVString(url)
+    url = webidl.converters.USVString(url, prefix, 'url')
     protocols = options.protocols
 
     // 1. Let baseURL be this's relevant settings object's API base URL.
@@ -159,12 +160,14 @@ class WebSocket extends EventTarget {
   close (code = undefined, reason = undefined) {
     webidl.brandCheck(this, WebSocket)
 
+    const prefix = 'WebSocket.close'
+
     if (code !== undefined) {
-      code = webidl.converters['unsigned short'](code, { clamp: true })
+      code = webidl.converters['unsigned short'](code, prefix, 'code', { clamp: true })
     }
 
     if (reason !== undefined) {
-      reason = webidl.converters.USVString(reason)
+      reason = webidl.converters.USVString(reason, prefix, 'reason')
     }
 
     // 1. If code is present, but is neither an integer equal to 1000 nor an
@@ -264,9 +267,10 @@ class WebSocket extends EventTarget {
   send (data) {
     webidl.brandCheck(this, WebSocket)
 
-    webidl.argumentLengthCheck(arguments, 1, { header: 'WebSocket.send' })
+    const prefix = 'WebSocket.send'
+    webidl.argumentLengthCheck(arguments, 1, prefix)
 
-    data = webidl.converters.WebSocketSendData(data)
+    data = webidl.converters.WebSocketSendData(data, prefix, 'data')
 
     // 1. If this's ready state is CONNECTING, then throw an
     //    "InvalidStateError" DOMException.
@@ -595,12 +599,12 @@ webidl.converters['sequence<DOMString>'] = webidl.sequenceConverter(
   webidl.converters.DOMString
 )
 
-webidl.converters['DOMString or sequence<DOMString>'] = function (V) {
+webidl.converters['DOMString or sequence<DOMString>'] = function (V, prefix, argument) {
   if (webidl.util.Type(V) === 'Object' && Symbol.iterator in V) {
     return webidl.converters['sequence<DOMString>'](V)
   }
 
-  return webidl.converters.DOMString(V)
+  return webidl.converters.DOMString(V, prefix, argument)
 }
 
 // This implements the propsal made in https://github.com/whatwg/websockets/issues/42
@@ -608,16 +612,12 @@ webidl.converters.WebSocketInit = webidl.dictionaryConverter([
   {
     key: 'protocols',
     converter: webidl.converters['DOMString or sequence<DOMString>'],
-    get defaultValue () {
-      return []
-    }
+    defaultValue: () => new Array(0)
   },
   {
     key: 'dispatcher',
     converter: (V) => V,
-    get defaultValue () {
-      return getGlobalDispatcher()
-    }
+    defaultValue: () => getGlobalDispatcher()
   },
   {
     key: 'headers',
diff --git a/test/fetch/headers.js b/test/fetch/headers.js
index ac1183eeded..91ba61f6e23 100644
--- a/test/fetch/headers.js
+++ b/test/fetch/headers.js
@@ -27,7 +27,7 @@ test('Headers initialization', async (t) => {
       throws(() => new Headers(['undici', 'fetch', 'fetch']), TypeError)
       throws(
         () => new Headers([0, 1, 2]),
-        TypeError('Sequence: Value of type Number is not an Object.')
+        TypeError('Headers contructor: init (0) is not an Object.')
       )
     })
 
@@ -42,7 +42,7 @@ test('Headers initialization', async (t) => {
       const init = ['undici', 'fetch', 'fetch', 'undici']
       throws(
         () => new Headers(init),
-        TypeError('Sequence: Value of type String is not an Object.')
+        TypeError('Headers contructor: init ("undici") is not an Object.')
       )
     })
   })
diff --git a/test/webidl/converters.js b/test/webidl/converters.js
index f39c05a8d7b..c5f4ce88d71 100644
--- a/test/webidl/converters.js
+++ b/test/webidl/converters.js
@@ -12,19 +12,19 @@ test('sequence', () => {
   assert.deepStrictEqual(converter([1, 2, 3]), ['1', '2', '3'])
 
   assert.throws(() => {
-    converter(3)
+    converter(3, 'converter', 'converter')
   }, TypeError, 'disallows non-objects')
 
   assert.throws(() => {
-    converter(null)
+    converter(null, 'converter', 'converter')
   }, TypeError)
 
   assert.throws(() => {
-    converter(undefined)
+    converter(undefined, 'converter', 'converter')
   }, TypeError)
 
   assert.throws(() => {
-    converter({})
+    converter({}, 'converter', 'converter')
   }, TypeError, 'no Symbol.iterator')
 
   assert.throws(() => {
@@ -40,7 +40,7 @@ test('sequence', () => {
           next: 'never!'
         }
       }
-    }))
+    }), 'converter', 'converter')
   }, TypeError, 'invalid generator')
 })
 
@@ -49,12 +49,12 @@ describe('webidl.dictionaryConverter', () => {
     const converter = webidl.dictionaryConverter([])
 
     assert.throws(() => {
-      converter(true)
+      converter(true, 'converter', 'converter')
     }, TypeError)
 
     for (const value of [{}, undefined, null]) {
       assert.doesNotThrow(() => {
-        converter(value)
+        converter(value, 'converter', 'converter')
       })
     }
   })
@@ -69,47 +69,47 @@ describe('webidl.dictionaryConverter', () => {
     ])
 
     assert.throws(() => {
-      converter({ wrongKey: 'key' })
+      converter({ wrongKey: 'key' }, 'converter', 'converter')
     }, TypeError)
 
     assert.doesNotThrow(() => {
-      converter({ Key: 'this key was required!' })
+      converter({ Key: 'this key was required!' }, 'converter', 'converter')
     })
   })
 })
 
 test('ArrayBuffer', () => {
   assert.throws(() => {
-    webidl.converters.ArrayBuffer(true)
+    webidl.converters.ArrayBuffer(true, 'converter', 'converter')
   }, TypeError)
 
   assert.throws(() => {
-    webidl.converters.ArrayBuffer({})
+    webidl.converters.ArrayBuffer({}, 'converter', 'converter')
   }, TypeError)
 
   assert.throws(() => {
     const sab = new SharedArrayBuffer(1024)
-    webidl.converters.ArrayBuffer(sab, { allowShared: false })
+    webidl.converters.ArrayBuffer(sab, 'converter', 'converter', { allowShared: false })
   }, TypeError)
 
   assert.doesNotThrow(() => {
     const sab = new SharedArrayBuffer(1024)
-    webidl.converters.ArrayBuffer(sab)
+    webidl.converters.ArrayBuffer(sab, 'converter', 'converter')
   })
 
   assert.doesNotThrow(() => {
     const ab = new ArrayBuffer(8)
-    webidl.converters.ArrayBuffer(ab)
+    webidl.converters.ArrayBuffer(ab, 'converter', 'converter')
   })
 })
 
 test('TypedArray', () => {
   assert.throws(() => {
-    webidl.converters.TypedArray(3)
+    webidl.converters.TypedArray(3, 'converter', 'converter')
   }, TypeError)
 
   assert.throws(() => {
-    webidl.converters.TypedArray({})
+    webidl.converters.TypedArray({}, 'converter', 'converter')
   }, TypeError)
 
   assert.throws(() => {
@@ -120,7 +120,7 @@ test('TypedArray', () => {
       }
     })
 
-    webidl.converters.TypedArray(uint8, Uint8Array, {
+    webidl.converters.TypedArray(uint8, Uint8Array, 'converter', 'converter', {
       allowShared: false
     })
   }, TypeError)
@@ -128,11 +128,11 @@ test('TypedArray', () => {
 
 test('DataView', () => {
   assert.throws(() => {
-    webidl.converters.DataView(3)
+    webidl.converters.DataView(3, 'converter', 'converter')
   }, TypeError)
 
   assert.throws(() => {
-    webidl.converters.DataView({})
+    webidl.converters.DataView({}, 'converter', 'converter')
   }, TypeError)
 
   assert.throws(() => {
@@ -145,7 +145,7 @@ test('DataView', () => {
       }
     })
 
-    webidl.converters.DataView(view, {
+    webidl.converters.DataView(view, 'converter', 'converter', {
       allowShared: false
     })
   })
@@ -153,7 +153,7 @@ test('DataView', () => {
   const buffer = new ArrayBuffer(16)
   const view = new DataView(buffer, 0)
 
-  assert.equal(webidl.converters.DataView(view), view)
+  assert.equal(webidl.converters.DataView(view, 'converter', 'converter'), view)
 })
 
 test('BufferSource', () => {
@@ -161,23 +161,23 @@ test('BufferSource', () => {
     const buffer = new ArrayBuffer(16)
     const view = new DataView(buffer, 0)
 
-    webidl.converters.BufferSource(view)
+    webidl.converters.BufferSource(view, 'converter', 'converter')
   })
 
   assert.throws(() => {
-    webidl.converters.BufferSource(3)
+    webidl.converters.BufferSource(3, 'converter', 'converter')
   }, TypeError)
 })
 
 test('ByteString', () => {
   assert.doesNotThrow(() => {
-    webidl.converters.ByteString('')
+    webidl.converters.ByteString('', 'converter', 'converter')
   })
 
   // https://github.com/nodejs/undici/issues/1590
   assert.throws(() => {
     const char = String.fromCharCode(256)
-    webidl.converters.ByteString(`invalid${char}char`)
+    webidl.converters.ByteString(`invalid${char}char`, 'converter', 'converter')
   }, {
     message: 'Cannot convert argument to a ByteString because the character at ' +
              'index 7 has a value of 256 which is greater than 255.'
diff --git a/test/webidl/errors.js b/test/webidl/errors.js
new file mode 100644
index 00000000000..11449fbfd60
--- /dev/null
+++ b/test/webidl/errors.js
@@ -0,0 +1,23 @@
+'use strict'
+
+const { test } = require('node:test')
+const assert = require('node:assert')
+const { Headers } = require('../..')
+
+test('ByteString', (t) => {
+  const name = Symbol('')
+  const value = Symbol('')
+
+  for (const method of [
+    'get',
+    'set',
+    'delete',
+    'append',
+    'has'
+  ]) {
+    assert.throws(
+      () => new Headers()[method](name, value),
+      new TypeError(`Headers.${method}: name is a symbol, which cannot be converted to a DOMString.`)
+    )
+  }
+})
diff --git a/test/webidl/helpers.js b/test/webidl/helpers.js
index b18baa5fb7b..fcd375f68b4 100644
--- a/test/webidl/helpers.js
+++ b/test/webidl/helpers.js
@@ -11,11 +11,11 @@ test('webidl.interfaceConverter', () => {
   const converter = webidl.interfaceConverter(A)
 
   assert.throws(() => {
-    converter(new B())
+    converter(new B(), 'converter', 'converter')
   }, TypeError)
 
   assert.doesNotThrow(() => {
-    converter(new A())
+    converter(new A(), 'converter', 'converter')
   })
 })
 
@@ -38,7 +38,7 @@ describe('webidl.dictionaryConverter', () => {
         get value () {
           return 6
         }
-      }),
+      }, 'converter', 'converter'),
       { key: 'string' }
     )
   })
@@ -52,7 +52,7 @@ describe('webidl.dictionaryConverter', () => {
       }
     ])
 
-    assert.deepStrictEqual(converter({ key: null }), { key: 0 })
+    assert.deepStrictEqual(converter({ key: null }, 'converter', 'converter'), { key: 0 })
   })
 
   test('no defaultValue and optional', () => {
@@ -63,6 +63,6 @@ describe('webidl.dictionaryConverter', () => {
       }
     ])
 
-    assert.deepStrictEqual(converter({ a: 'b', c: 'd' }), {})
+    assert.deepStrictEqual(converter({ a: 'b', c: 'd' }, 'converter', 'converter'), {})
   })
 })
diff --git a/test/websocket/messageevent.js b/test/websocket/messageevent.js
index de3b6c5fc8e..b1381019c27 100644
--- a/test/websocket/messageevent.js
+++ b/test/websocket/messageevent.js
@@ -99,25 +99,25 @@ test('test/parallel/test-worker-message-port.js', () => {
 
   assert.throws(() => new MessageEvent('message', { source: 1 }), {
     constructor: TypeError,
-    message: 'MessagePort: Expected 1 to be an instance of MessagePort.'
+    message: 'MessageEvent constructor: Expected eventInitDict ("1") to be an instance of MessagePort.'
   })
   assert.throws(() => new MessageEvent('message', { source: {} }), {
     constructor: TypeError,
-    message: 'MessagePort: Expected {} to be an instance of MessagePort.'
+    message: 'MessageEvent constructor: Expected eventInitDict ("{}") to be an instance of MessagePort.'
   })
   assert.throws(() => new MessageEvent('message', { ports: 0 }), {
     constructor: TypeError,
-    message: 'Sequence: Value of type Number is not an Object.'
+    message: 'MessageEvent constructor: eventInitDict (0) is not an Object.'
   })
   assert.throws(() => new MessageEvent('message', { ports: [null] }), {
     constructor: TypeError,
-    message: 'MessagePort: Expected null to be an instance of MessagePort.'
+    message: 'MessageEvent constructor: Expected eventInitDict ("null") to be an instance of MessagePort.'
   })
   assert.throws(() =>
     new MessageEvent('message', { ports: [{}] })
   , {
     constructor: TypeError,
-    message: 'MessagePort: Expected {} to be an instance of MessagePort.'
+    message: 'MessageEvent constructor: Expected eventInitDict ("{}") to be an instance of MessagePort.'
   })
 
   assert(new MessageEvent('message') instanceof Event)
diff --git a/types/webidl.d.ts b/types/webidl.d.ts
index 1e362d6f40d..fe802a20124 100644
--- a/types/webidl.d.ts
+++ b/types/webidl.d.ts
@@ -55,7 +55,9 @@ interface WebidlUtil {
     V: unknown,
     bitLength: number,
     signedness: 'signed' | 'unsigned',
-    opts?: ConvertToIntOpts
+    opts?: ConvertToIntOpts,
+    prefix: string,
+    argument: string
   ): number
 
   /**
@@ -73,14 +75,14 @@ interface WebidlConverters {
   /**
    * @see https://webidl.spec.whatwg.org/#es-DOMString
    */
-  DOMString (V: unknown, opts?: {
+  DOMString (V: unknown, prefix: string, argument: string, opts?: {
     legacyNullToEmptyString: boolean
   }): string
 
   /**
    * @see https://webidl.spec.whatwg.org/#es-ByteString
    */
-  ByteString (V: unknown): string
+  ByteString (V: unknown, prefix: string, argument: string): string
 
   /**
    * @see https://webidl.spec.whatwg.org/#es-USVString
@@ -204,7 +206,7 @@ export interface Webidl {
    */
   dictionaryConverter (converters: {
     key: string,
-    defaultValue?: unknown,
+    defaultValue?: () => unknown,
     required?: boolean,
     converter: (...args: unknown[]) => unknown,
     allowedValues?: unknown[]
@@ -218,8 +220,5 @@ export interface Webidl {
     converter: Converter<T>
   ): (V: unknown) => ReturnType<typeof converter> | null
 
-  argumentLengthCheck (args: { length: number }, min: number, context: {
-    header: string
-    message?: string
-  }): void
+  argumentLengthCheck (args: { length: number }, min: number, context: string): void
 }