diff --git a/extensions/broadcast_channel/01_broadcast_channel.js b/extensions/broadcast_channel/01_broadcast_channel.js
index cab4fa41cd0729..c921132fab288c 100644
--- a/extensions/broadcast_channel/01_broadcast_channel.js
+++ b/extensions/broadcast_channel/01_broadcast_channel.js
@@ -4,6 +4,7 @@
 ((window) => {
   const core = window.Deno.core;
   const webidl = window.__bootstrap.webidl;
+  const { setTarget } = window.__bootstrap.event;
 
   const handlerSymbol = Symbol("eventHandlers");
   function makeWrappedHandler(handler) {
@@ -21,7 +22,10 @@
     // HTML specification section 8.1.5.1
     Object.defineProperty(emitter, `on${name}`, {
       get() {
-        return this[handlerSymbol]?.get(name)?.handler;
+        // TODO(bnoordhuis) The "BroadcastChannel should have an onmessage
+        // event" WPT test expects that .onmessage !== undefined. Returning
+        // null makes it pass but is perhaps not exactly in the spirit.
+        return this[handlerSymbol]?.get(name)?.handler ?? null;
       },
       set(value) {
         if (!this[handlerSymbol]) {
@@ -81,14 +85,23 @@
         throw new DOMException("Already closed", "InvalidStateError");
       }
 
+      const prefix = "Failed to execute 'postMessage' on 'BroadcastChannel'";
+      webidl.requiredArguments(arguments.length, 1, { prefix });
+
+      if (typeof message === "function" || typeof message === "symbol") {
+        throw new DOMException("Uncloneable value", "DataCloneError");
+      }
+
       core.opAsync("op_broadcast_send", this[_rid], core.serialize(message));
     }
 
     close() {
       webidl.assertBranded(this, BroadcastChannel);
 
+      const closed = this[_closed];
       this[_closed] = true;
-      core.close(this[_rid]);
+
+      if (!closed) core.close(this[_rid]);
     }
 
     async #eventLoop() {
@@ -102,11 +115,13 @@
           return;
         }
 
+        const location = window.location;
+
         const event = new MessageEvent("message", {
           data: core.deserialize(new Uint8Array(message)),
-          origin: window.location,
+          origin: location.protocol + "//" + location.host,
         });
-        event.target = this;
+        setTarget(event, this);
 
         this.dispatchEvent(event);
       }
diff --git a/extensions/broadcast_channel/lib.rs b/extensions/broadcast_channel/lib.rs
index 62a31aed9d3456..614474495f6924 100644
--- a/extensions/broadcast_channel/lib.rs
+++ b/extensions/broadcast_channel/lib.rs
@@ -132,13 +132,12 @@ pub async fn op_broadcast_next_event<B: BroadcastChannel + 'static>(
   rid: ResourceId,
   _bufs: Option<ZeroCopyBuf>,
 ) -> Result<Option<Vec<u8>>, AnyError> {
-  let resource = state
-    .borrow()
-    .resource_table
-    .get::<B::Resource>(rid)
-    .ok_or_else(bad_resource_id)?;
+  let resource = state.borrow().resource_table.get::<B::Resource>(rid);
 
-  B::next_event(&resource).await
+  match resource {
+    Some(resource) => B::next_event(&resource).await,
+    None => Ok(None),
+  }
 }
 
 pub fn init<B: BroadcastChannel + 'static>() -> Extension {
diff --git a/extensions/web/02_event.js b/extensions/web/02_event.js
index 35112132e05a21..2b6d3a0e491452 100644
--- a/extensions/web/02_event.js
+++ b/extensions/web/02_event.js
@@ -1117,6 +1117,10 @@
   }
 
   class MessageEvent extends Event {
+    get source() {
+      return null;
+    }
+
     constructor(type, eventInitDict) {
       super(type, {
         bubbles: eventInitDict?.bubbles ?? false,
@@ -1208,5 +1212,6 @@
   };
   window.__bootstrap.event = {
     setIsTrusted,
+    setTarget,
   };
 })(this);
diff --git a/tools/wpt.ts b/tools/wpt.ts
index 12e9047a488693..327899e80165dc 100755
--- a/tools/wpt.ts
+++ b/tools/wpt.ts
@@ -506,21 +506,32 @@ function discoverTestsToRun(
           continue;
         }
 
-        for (
-          const [path, options] of entry.slice(
-            1,
-          ) as ManifestTestVariation[]
-        ) {
-          if (!path) continue;
-          const url = new URL(path, "http://web-platform.test:8000");
-          if (!url.pathname.endsWith(".any.html")) continue;
+        if (key.endsWith(".html")) {
+          const url = new URL(sourcePath, "http://web-platform.test:8000");
           testsToRun.push({
             sourcePath,
             path: url.pathname + url.search,
             url,
-            options,
+            options: {},
             expectation,
           });
+        } else {
+          for (
+            const [path, options] of entry.slice(
+              1,
+            ) as ManifestTestVariation[]
+          ) {
+            if (!path) continue;
+            const url = new URL(path, "http://web-platform.test:8000");
+            if (!url.pathname.endsWith(".any.html")) continue;
+            testsToRun.push({
+              sourcePath,
+              path: url.pathname + url.search,
+              url,
+              options,
+              expectation,
+            });
+          }
         }
       } else {
         walk(entry, expectation, sourcePath);
diff --git a/tools/wpt/expectation.json b/tools/wpt/expectation.json
index 6eec573cb89d61..84d46814045f48 100644
--- a/tools/wpt/expectation.json
+++ b/tools/wpt/expectation.json
@@ -1064,6 +1064,12 @@
       }
     }
   },
+  "webmessaging": {
+    "broadcastchannel": {
+      "basics.html": true,
+      "interface.html": true
+    }
+  },
   "xhr": {
     "formdata": {
       "append.any.js": true,