diff --git a/browser/components/customizableui/test/browser_940307_panel_click_closure_handling.js b/browser/components/customizableui/test/browser_940307_panel_click_closure_handling.js
index cb28a3c9dd4c..3c870b12c66d 100644
--- a/browser/components/customizableui/test/browser_940307_panel_click_closure_handling.js
+++ b/browser/components/customizableui/test/browser_940307_panel_click_closure_handling.js
@@ -101,6 +101,7 @@ add_task(function*() {
   ok(!isPanelUIOpen(), "Panel should no longer be open");
 
   Services.prefs.setBoolPref("browser.search.suggest.enabled", suggestEnabled);
+  CustomizableUI.reset();
 });
 
 add_task(function*() {
diff --git a/toolkit/components/search/SearchSuggestionController.jsm b/toolkit/components/search/SearchSuggestionController.jsm
index f312e85e927a..8109fbb35849 100644
--- a/toolkit/components/search/SearchSuggestionController.jsm
+++ b/toolkit/components/search/SearchSuggestionController.jsm
@@ -318,7 +318,13 @@ this.SearchSuggestionController.prototype = {
    * @return {Object}
    */
   _dedupeAndReturnResults: function(suggestResults) {
-    NS_ASSERT(this._searchString !== null, "this._searchString shouldn't be null when returning results");
+    if (this._searchString === null) {
+      // _searchString can be null if stop() was called and remote suggestions
+      // were disabled (stopping if we are fetching remote suggestions will
+      // cause a promise rejection before we reach _dedupeAndReturnResults).
+      return null;
+    }
+
     let results = {
       term: this._searchString,
       remote: [],