diff --git a/packages/koishi-core/src/meta.ts b/packages/koishi-core/src/meta.ts
index 941c2b682e..b0f32b16e4 100644
--- a/packages/koishi-core/src/meta.ts
+++ b/packages/koishi-core/src/meta.ts
@@ -1,4 +1,4 @@
-import { User, Group, UserField, GroupField } from './database'
+import { User, Group } from './database'
 import { ParsedCommandLine } from './command'
 import { isInteger } from 'koishi-utils'
 
diff --git a/packages/koishi-utils/src/observe.ts b/packages/koishi-utils/src/observe.ts
index ba1ae0e17a..b6b5d9dbee 100644
--- a/packages/koishi-utils/src/observe.ts
+++ b/packages/koishi-utils/src/observe.ts
@@ -8,13 +8,12 @@ const builtinClasses = ['Date', 'RegExp', 'Set', 'Map', 'WeakSet', 'WeakMap', 'A
 const refs: Record<string | number, any> = {}
 
 function observeObject <T extends object> (target: T, label: string, update?: () => void): T {
-  Object.defineProperty(target, '__proxyGetters__', { value: {} })
+  if (!target['__proxyGetters__']) {
+    Object.defineProperty(target, '__proxyGetters__', { value: {} })
+  }
 
   if (!update) {
-    Object.defineProperty(target, '_diff', {
-      value: {},
-      writable: true,
-    })
+    Object.defineProperty(target, '_diff', { value: {}, writable: true })
   }
 
   return new Proxy(target as Observed<T, any>, {
diff --git a/packages/plugin-teach/src/internal.ts b/packages/plugin-teach/src/internal.ts
index 4ba17941c8..b53e3cbe80 100644
--- a/packages/plugin-teach/src/internal.ts
+++ b/packages/plugin-teach/src/internal.ts
@@ -1,6 +1,35 @@
 import { Context } from 'koishi-core'
 import { DialogueFlag } from './database'
-import { simplifyQuestion, simplifyAnswer } from './utils'
+import { simplify } from 'koishi-utils'
+
+const prefixPunctuation = /^([()\]]|\[(?!cq:))*/
+const suffixPunctuation = /([.,?!()[~]|(?<!\[cq:[^\]]+)\])*$/
+
+export function stripPunctuation (source: string) {
+  source = source.toLowerCase()
+    .replace(/\s+/g, '')
+    .replace(/，/g, ',')
+    .replace(/、/g, ',')
+    .replace(/。/g, '.')
+    .replace(/？/g, '?')
+    .replace(/！/g, '!')
+    .replace(/（/g, '(')
+    .replace(/）/g, ')')
+    .replace(/【/g, '[')
+    .replace(/】/g, ']')
+    .replace(/～/g, '~')
+  return source
+    .replace(prefixPunctuation, '')
+    .replace(suffixPunctuation, '') || source
+}
+
+export function simplifyQuestion (source: string) {
+  return simplify(stripPunctuation(String(source || '')))
+}
+
+export function simplifyAnswer (source: string) {
+  return (String(source || '')).trim()
+}
 
 export default function apply (ctx: Context) {
   ctx.command('teach')
@@ -75,5 +104,6 @@ export default function apply (ctx: Context) {
   ctx.on('dialogue/receive', (meta, test) => {
     if (meta.message.includes('[CQ:image,')) return true
     test.question = simplifyQuestion(meta.message)
+    return !test.question
   })
 }
diff --git a/packages/plugin-teach/src/receiver.ts b/packages/plugin-teach/src/receiver.ts
index 0cbd93d162..dbd13f32c5 100644
--- a/packages/plugin-teach/src/receiver.ts
+++ b/packages/plugin-teach/src/receiver.ts
@@ -1,6 +1,6 @@
 import { Context, UserField, getSenderName, Meta } from 'koishi-core'
 import { CQCode, sleep } from 'koishi-utils'
-import { simplifyQuestion, getDialogues } from './utils'
+import { getDialogues } from './utils'
 import { Dialogue, DialogueTest } from './database'
 
 declare module 'koishi-core/dist/context' {
diff --git a/packages/plugin-teach/src/utils.ts b/packages/plugin-teach/src/utils.ts
index 1e010d96bc..2b094991dd 100644
--- a/packages/plugin-teach/src/utils.ts
+++ b/packages/plugin-teach/src/utils.ts
@@ -1,5 +1,5 @@
 import { Context, Meta, User } from 'koishi-core'
-import { simplify, difference } from 'koishi-utils'
+import { difference } from 'koishi-utils'
 import { Dialogue, DialogueTest } from './database'
 import { SessionState } from './receiver'
 
@@ -17,40 +17,7 @@ declare module 'koishi-core/dist/context' {
   }
 }
 
-export interface TeachConfig {
-  key?: string
-  imageServer?: string
-  uploadServer?: string
-}
-
-const prefixPunctuation = /^([()\]]|\[(?!cq:))*/
-const suffixPunctuation = /([.,?!()[~]|(?<!\[cq:[^\]]+)\])*$/
-
-export function stripPunctuation (source: string) {
-  source = source.toLowerCase()
-    .replace(/\s+/g, '')
-    .replace(/，/g, ',')
-    .replace(/、/g, ',')
-    .replace(/。/g, '.')
-    .replace(/？/g, '?')
-    .replace(/！/g, '!')
-    .replace(/（/g, '(')
-    .replace(/）/g, ')')
-    .replace(/【/g, '[')
-    .replace(/】/g, ']')
-    .replace(/～/g, '~')
-  return source
-    .replace(prefixPunctuation, '')
-    .replace(suffixPunctuation, '') || source
-}
-
-export function simplifyQuestion (source: string) {
-  return simplify(stripPunctuation(String(source || '')))
-}
-
-export function simplifyAnswer (source: string) {
-  return (String(source || '')).trim()
-}
+export interface TeachConfig {}
 
 export function deleteDuplicate <T> (array: T[]) {
   return [...new Set(array)]