diff --git a/app/assets/javascripts/discourse/controllers/topic.js.es6 b/app/assets/javascripts/discourse/controllers/topic.js.es6
index 7a4bc0535d2..11f4fe4cba1 100644
--- a/app/assets/javascripts/discourse/controllers/topic.js.es6
+++ b/app/assets/javascripts/discourse/controllers/topic.js.es6
@@ -16,6 +16,10 @@ import { userPath } from 'discourse/lib/url';
 
 const customPostMessageCallbacks = {};
 
+export function resetCustomPostMessageCallbacks() {
+  customPostMessageCallbacks = {};
+}
+
 export function registerCustomPostMessageCallback(type, callback) {
   if (customPostMessageCallbacks[type]) {
     throw `Error ${type} is an already registered post message!`;
diff --git a/test/javascripts/helpers/qunit-helpers.js.es6 b/test/javascripts/helpers/qunit-helpers.js.es6
index 1a267c8c435..50bf08bef0d 100644
--- a/test/javascripts/helpers/qunit-helpers.js.es6
+++ b/test/javascripts/helpers/qunit-helpers.js.es6
@@ -10,6 +10,7 @@ import { flushMap } from 'discourse/models/store';
 import { clearRewrites } from 'discourse/lib/url';
 import { initSearchData } from 'discourse/widgets/search-menu';
 import { resetDecorators } from 'discourse/widgets/widget';
+import { resetCustomPostMessageCallbacks } from 'discourse/controllers/topic';
 
 export function currentUser() {
   return Discourse.User.create(sessionFixtures['/session/current.json'].current_user);
@@ -107,6 +108,7 @@ export function acceptance(name, options) {
       clearRewrites();
       initSearchData();
       resetDecorators();
+      resetCustomPostMessageCallbacks();
       Discourse.reset();
     }
   });