diff --git a/toolkit/mozapps/extensions/content/extensions.js b/toolkit/mozapps/extensions/content/extensions.js
index b21ffdeb870..bccaa0eb15c 100644
--- a/toolkit/mozapps/extensions/content/extensions.js
+++ b/toolkit/mozapps/extensions/content/extensions.js
@@ -437,16 +437,19 @@ var gEventManager = {
       contextMenu.setAttribute("addontype", addon.type);
 
       var menuSep = document.getElementById("addonitem-menuseparator");
-      var countEnabledMenuCmds = 0;
+      var countMenuItemsBeforeSep = 0;
       for (let child of contextMenu.children) {
+        if (child == menuSep) {
+          break;
+        }
         if (child.nodeName == "menuitem" &&
           gViewController.isCommandEnabled(child.command)) {
-            countEnabledMenuCmds++;
+            countMenuItemsBeforeSep++;
         }
       }
 
-      // with only one menu item, we hide the menu separator
-      menuSep.hidden = (countEnabledMenuCmds <= 1);
+      // Hide the separator if there are no visible menu items before it
+      menuSep.hidden = (countMenuItemsBeforeSep == 0);
 
     }, false);
   },
diff --git a/toolkit/mozapps/extensions/test/browser/browser_openH264.js b/toolkit/mozapps/extensions/test/browser/browser_openH264.js
index 4a8d9bc23a1..1bee700b066 100644
--- a/toolkit/mozapps/extensions/test/browser/browser_openH264.js
+++ b/toolkit/mozapps/extensions/test/browser/browser_openH264.js
@@ -197,6 +197,21 @@ add_task(function* testInstalledDetails() {
   el = doc.getElementById("detail-warning");
   is_element_hidden(el, "Warning notification is hidden.");
   el = doc.getElementsByTagName("setting")[0];
+
+  let contextMenu = doc.getElementById("addonitem-popup");
+  let deferred = Promise.defer();
+  let listener = () => {
+    contextMenu.removeEventListener("popupshown", listener, false);
+    deferred.resolve();
+  };
+  contextMenu.addEventListener("popupshown", listener, false);
+  el = doc.getElementsByClassName("detail-view-container")[0];
+  EventUtils.synthesizeMouse(el, 4, 4, { }, gManagerWindow);
+  EventUtils.synthesizeMouse(el, 4, 4, { type: "contextmenu", button: 2 }, gManagerWindow);
+  yield deferred.promise;
+  let menuSep = doc.getElementById("addonitem-menuseparator");
+  is_element_hidden(menuSep, "Menu separator is hidden.");
+  contextMenu.hidePopup();
 });
 
 add_task(function* testPreferencesButton() {