diff --git a/src/mixins/notify.js b/src/mixins/notify.js
index a835f16..35bf28d 100644
--- a/src/mixins/notify.js
+++ b/src/mixins/notify.js
@@ -1,6 +1,4 @@
-import Emitter from '../emitter'
-
-type callback = (input?: mixed) => void
+import Emitter, { callback } from '../emitter'
 
 export default function notify(superclass: Emitter): Emitter {
   return class extends superclass {
diff --git a/src/mixins/notify.test.js b/src/mixins/notify.test.js
index 2ee0014..1ead5b3 100644
--- a/src/mixins/notify.test.js
+++ b/src/mixins/notify.test.js
@@ -1,11 +1,9 @@
 import Emitter from '../emitter'
 import notify from './notify'
 
-class E extends notify(Emitter) {}
-
 describe('notify', function() {
   beforeEach(() => {
-    this.emitter = new E()
+    this.emitter = new (notify(Emitter))()
   })
 
   it('should return a new constructor wrapping the argument', () => {