--- a/browser/components/extensions/ext-contextMenus.js
+++ b/browser/components/extensions/ext-contextMenus.js
@@ -449,26 +449,26 @@ MenuItem.prototype = {
     return true;
   },
 };
 
 var gExtensionCount = 0;
 /* eslint-disable mozilla/balanced-listeners */
 extensions.on("startup", (type, extension) => {
   gContextMenuMap.set(extension, new Map());
-  gRootItems.delete(extension);
   if (++gExtensionCount == 1) {
     Services.obs.addObserver(contextMenuObserver,
                              "on-build-contextmenu",
                              false);
   }
 });
 
 extensions.on("shutdown", (type, extension) => {
   gContextMenuMap.delete(extension);
+  gRootItems.delete(extension);
   if (--gExtensionCount == 0) {
     Services.obs.removeObserver(contextMenuObserver,
                                 "on-build-contextmenu");
   }
 });
 /* eslint-enable mozilla/balanced-listeners */
 
 extensions.registerSchemaAPI("contextMenus", (extension, context) => {