diff --git a/test/unit/modules/observer/observer.spec.js b/test/unit/modules/observer/observer.spec.js
index b7f59fedb02..a479b497acd 100644
--- a/test/unit/modules/observer/observer.spec.js
+++ b/test/unit/modules/observer/observer.spec.js
@@ -318,6 +318,7 @@ describe('Observer', () => {
 
   it('Cannot enable reactivity on a property that is already defined', done => {
     const vm = new Vue({
+      template: '<div></div>',
       data: {
         person: {
           age: 32