diff --git a/packages/utils/deep-assign.ts b/packages/utils/deep-assign.ts
index 3b5f592a3..e2a4653e9 100644
--- a/packages/utils/deep-assign.ts
+++ b/packages/utils/deep-assign.ts
@@ -11,7 +11,7 @@ function assignKey(to: ObjectIndex, from: ObjectIndex, key: string) {
     return;
   }
 
-  if (!hasOwnProperty.call(to, key) || !isObj(val)) {
+  if (!hasOwnProperty.call(to, key) || !isObj(val) || typeof val === 'function') {
     to[key] = val;
   } else {
     to[key] = deepAssign(Object(to[key]), from[key]);
diff --git a/packages/utils/test/index.spec.js b/packages/utils/test/index.spec.js
index d2bebae65..0b8ff6432 100644
--- a/packages/utils/test/index.spec.js
+++ b/packages/utils/test/index.spec.js
@@ -1,4 +1,5 @@
 import { deepClone } from '../deep-clone';
+import { deepAssign } from '../deep-assign';
 import { isDef, get } from '..';
 import { raf, cancelRaf } from '../dom/raf';
 import { later } from '../../../test/utils';
@@ -11,7 +12,7 @@ import { camelize } from '../format/string';
 test('deepClone', () => {
   const a = { foo: 0 };
   const b = { foo: 0, bar: 1 };
-  const fn = () => { };
+  const fn = () => {};
   const arr = [a, b];
   expect(deepClone(a)).toEqual(a);
   expect(deepClone(b)).toEqual(b);
@@ -21,13 +22,30 @@ test('deepClone', () => {
   expect(deepClone(1)).toEqual(1);
 });
 
+test('deepAssign', () => {
+  const fn = () => {};
+
+  expect(deepAssign({}, { foo: null })).toEqual({});
+  expect(deepAssign({}, { foo: undefined })).toEqual({});
+  expect(deepAssign({ fn: null }, { fn })).toEqual({ fn });
+  expect(deepAssign({ foo: 0 }, { bar: 1 })).toEqual({ foo: 0, bar: 1 });
+  expect(deepAssign({ foo: { bar: false } }, { foo: { bar: true, foo: false } })).toEqual(
+    {
+      foo: {
+        bar: true,
+        foo: false
+      }
+    }
+  );
+});
+
 test('isDef', () => {
   expect(isDef(null)).toBeFalsy();
   expect(isDef(undefined)).toBeFalsy();
   expect(isDef(1)).toBeTruthy();
   expect(isDef('1')).toBeTruthy();
   expect(isDef({})).toBeTruthy();
-  expect(isDef(() => { })).toBeTruthy();
+  expect(isDef(() => {})).toBeTruthy();
 });
 
 test('camelize', () => {