diff --git a/packages/reactivity/__tests__/reactiveArray.spec.ts b/packages/reactivity/__tests__/reactiveArray.spec.ts
index fabafc21e25..74357cb7295 100644
--- a/packages/reactivity/__tests__/reactiveArray.spec.ts
+++ b/packages/reactivity/__tests__/reactiveArray.spec.ts
@@ -725,5 +725,26 @@ describe('reactivity/reactive/Array', () => {
       expect(state.things.map('foo', 'bar', 'baz')).toEqual(['1', '2', '3'])
       expect(state.things.some('foo', 'bar', 'baz')).toBe(true)
     })
+
+    test('computed + extend methods', () => {
+      class Collection extends Array {
+        find(matcher: any) {
+          return super.find(matcher)
+        }
+      }
+
+      const state = reactive({
+        // @ts-expect-error
+        things: new Collection({ foo: '' }),
+      })
+
+      const bar = computed(() => {
+        return state.things.find((obj: any) => obj.foo === 'bar')
+      })
+      bar.value
+      state.things[0].foo = 'bar'
+
+      expect(bar.value).toEqual({ foo: 'bar' })
+    })
   })
 })
diff --git a/packages/reactivity/src/arrayInstrumentations.ts b/packages/reactivity/src/arrayInstrumentations.ts
index 6cf7602eca5..69f08d6c5d1 100644
--- a/packages/reactivity/src/arrayInstrumentations.ts
+++ b/packages/reactivity/src/arrayInstrumentations.ts
@@ -47,42 +47,42 @@ export const arrayInstrumentations: Record<string | symbol, Function> = <any>{
     fn: (item: unknown, index: number, array: unknown[]) => unknown,
     thisArg?: unknown,
   ) {
-    return apply(this, 'every', fn, thisArg, undefined, arguments)
+    return apply(this, 'every', fn, thisArg)
   },
 
   filter(
     fn: (item: unknown, index: number, array: unknown[]) => unknown,
     thisArg?: unknown,
   ) {
-    return apply(this, 'filter', fn, thisArg, v => v.map(toReactive), arguments)
+    return apply(this, 'filter', fn, thisArg, v => v.map(toReactive))
   },
 
   find(
     fn: (item: unknown, index: number, array: unknown[]) => boolean,
     thisArg?: unknown,
   ) {
-    return apply(this, 'find', fn, thisArg, toReactive, arguments)
+    return apply(this, 'find', fn, thisArg, toReactive)
   },
 
   findIndex(
     fn: (item: unknown, index: number, array: unknown[]) => boolean,
     thisArg?: unknown,
   ) {
-    return apply(this, 'findIndex', fn, thisArg, undefined, arguments)
+    return apply(this, 'findIndex', fn, thisArg)
   },
 
   findLast(
     fn: (item: unknown, index: number, array: unknown[]) => boolean,
     thisArg?: unknown,
   ) {
-    return apply(this, 'findLast', fn, thisArg, toReactive, arguments)
+    return apply(this, 'findLast', fn, thisArg, toReactive)
   },
 
   findLastIndex(
     fn: (item: unknown, index: number, array: unknown[]) => boolean,
     thisArg?: unknown,
   ) {
-    return apply(this, 'findLastIndex', fn, thisArg, undefined, arguments)
+    return apply(this, 'findLastIndex', fn, thisArg)
   },
 
   // flat, flatMap could benefit from ARRAY_ITERATE but are not straight-forward to implement
@@ -91,7 +91,7 @@ export const arrayInstrumentations: Record<string | symbol, Function> = <any>{
     fn: (item: unknown, index: number, array: unknown[]) => unknown,
     thisArg?: unknown,
   ) {
-    return apply(this, 'forEach', fn, thisArg, undefined, arguments)
+    return apply(this, 'forEach', fn, thisArg)
   },
 
   includes(...args: unknown[]) {
@@ -116,7 +116,7 @@ export const arrayInstrumentations: Record<string | symbol, Function> = <any>{
     fn: (item: unknown, index: number, array: unknown[]) => unknown,
     thisArg?: unknown,
   ) {
-    return apply(this, 'map', fn, thisArg, undefined, arguments)
+    return apply(this, 'map', fn, thisArg)
   },
 
   pop() {
@@ -161,7 +161,7 @@ export const arrayInstrumentations: Record<string | symbol, Function> = <any>{
     fn: (item: unknown, index: number, array: unknown[]) => unknown,
     thisArg?: unknown,
   ) {
-    return apply(this, 'some', fn, thisArg, undefined, arguments)
+    return apply(this, 'some', fn, thisArg)
   },
 
   splice(...args: unknown[]) {
@@ -227,7 +227,6 @@ function iterator(
 // higher than that
 type ArrayMethods = keyof Array<any> | 'findLast' | 'findLastIndex'
 
-const arrayProto = Array.prototype
 // instrument functions that read (potentially) all items
 // to take ARRAY_ITERATE dependency
 function apply(
@@ -236,20 +235,12 @@ function apply(
   fn: (item: unknown, index: number, array: unknown[]) => unknown,
   thisArg?: unknown,
   wrappedRetFn?: (result: any) => unknown,
-  args?: IArguments,
 ) {
   const arr = shallowReadArray(self)
-  const needsWrap = arr !== self && !isShallow(self)
-  // @ts-expect-error our code is limited to es2016 but user code is not
-  const methodFn = arr[method]
-  // @ts-expect-error
-  if (methodFn !== arrayProto[method]) {
-    const result = methodFn.apply(arr, args)
-    return needsWrap ? toReactive(result) : result
-  }
-
+  let needsWrap = false
   let wrappedFn = fn
   if (arr !== self) {
+    needsWrap = !isShallow(self)
     if (needsWrap) {
       wrappedFn = function (this: unknown, item, index) {
         return fn.call(this, toReactive(item), index, self)
@@ -260,7 +251,8 @@ function apply(
       }
     }
   }
-  const result = methodFn.call(arr, wrappedFn, thisArg)
+  // @ts-expect-error our code is limited to es2016 but user code is not
+  const result = arr[method](wrappedFn, thisArg)
   return needsWrap && wrappedRetFn ? wrappedRetFn(result) : result
 }
 
diff --git a/packages/reactivity/src/baseHandlers.ts b/packages/reactivity/src/baseHandlers.ts
index 5916c0b5d81..41c6936428c 100644
--- a/packages/reactivity/src/baseHandlers.ts
+++ b/packages/reactivity/src/baseHandlers.ts
@@ -86,7 +86,12 @@ class BaseReactiveHandler implements ProxyHandler<Target> {
 
     if (!isReadonly) {
       let fn: Function | undefined
-      if (targetIsArray && (fn = arrayInstrumentations[key])) {
+      if (
+        targetIsArray &&
+        // @ts-expect-error our code is limited to es2016 but user code is not
+        (target as any[])[key] === Array.prototype[key] &&
+        (fn = arrayInstrumentations[key])
+      ) {
         return fn
       }
       if (key === 'hasOwnProperty') {