diff --git a/src/core/instance/render-helpers/check-keycodes.js b/src/core/instance/render-helpers/check-keycodes.js
index c12402b1..02613d4d 100644
--- a/src/core/instance/render-helpers/check-keycodes.js
+++ b/src/core/instance/render-helpers/check-keycodes.js
@@ -31,4 +31,5 @@ export function checkKeyCodes (
   } else if (eventKeyName) {
     return hyphenate(eventKeyName) !== key
   }
+  return eventKeyCode === undefined
 }
diff --git a/test/unit/features/directives/on.spec.js b/test/unit/features/directives/on.spec.js
index 95693c19..7c252031 100644
--- a/test/unit/features/directives/on.spec.js
+++ b/test/unit/features/directives/on.spec.js
@@ -976,6 +976,17 @@ describe('Directive v-on', () => {
     expect(value).toBe(1)
   })
 
+  it('should not execute callback if modifiers are present', () => {
+    vm = new Vue({
+      el,
+      template: '<input @keyup.?="foo">',
+      methods: { foo: spy }
+    })
+    // simulating autocomplete event (Event object with type keyup but without keyCode)
+    triggerEvent(vm.$el, 'keyup')
+    expect(spy.calls.count()).toBe(0)
+  })
+
   describe('dynamic arguments', () => {
     it('basic', done => {
       const spy = jasmine.createSpy()