diff --git a/src/core/util/options.js b/src/core/util/options.js
index e3b1b718f54..53f96830165 100644
--- a/src/core/util/options.js
+++ b/src/core/util/options.js
@@ -1,6 +1,5 @@
 /* @flow */
 
-import Vue from '../instance/index'
 import config from '../config'
 import { warn } from './debug'
 import { set } from '../observer/index'
@@ -275,21 +274,20 @@ export function mergeOptions (
   if (process.env.NODE_ENV !== 'production') {
     checkComponents(child)
   }
+
+  if (typeof child === 'function') {
+    child = child.options
+  }
+
   normalizeProps(child)
   normalizeDirectives(child)
   const extendsFrom = child.extends
   if (extendsFrom) {
-    parent = typeof extendsFrom === 'function'
-      ? mergeOptions(parent, extendsFrom.options, vm)
-      : mergeOptions(parent, extendsFrom, vm)
+    parent = mergeOptions(parent, extendsFrom, vm)
   }
   if (child.mixins) {
     for (let i = 0, l = child.mixins.length; i < l; i++) {
-      let mixin = child.mixins[i]
-      if (mixin.prototype instanceof Vue) {
-        mixin = mixin.options
-      }
-      parent = mergeOptions(parent, mixin, vm)
+      parent = mergeOptions(parent, child.mixins[i], vm)
     }
   }
   const options = {}
diff --git a/test/unit/features/global-api/mixin.spec.js b/test/unit/features/global-api/mixin.spec.js
index e0ae7ce2439..f452dbed8d2 100644
--- a/test/unit/features/global-api/mixin.spec.js
+++ b/test/unit/features/global-api/mixin.spec.js
@@ -124,4 +124,21 @@ describe('Global API: mixin', () => {
     expect(Test.options.computed.$style()).toBe(123)
     expect(Test.options.beforeCreate).toEqual([mixinSpy, baseSpy, spy])
   })
+
+  // vue-class-component#83
+  it('should work for a constructor mixin', () => {
+    const spy = jasmine.createSpy('global mixin')
+    const Mixin = Vue.extend({
+      created () {
+        spy(this.$options.myOption)
+      }
+    })
+
+    Vue.mixin(Mixin)
+
+    new Vue({
+      myOption: 'hello'
+    })
+    expect(spy).toHaveBeenCalledWith('hello')
+  })
 })