diff --git a/widget/cocoa/nsChildView.mm b/widget/cocoa/nsChildView.mm
index 2ab284b9e150..7ca30bbe459f 100644
--- a/widget/cocoa/nsChildView.mm
+++ b/widget/cocoa/nsChildView.mm
@@ -5474,10 +5474,23 @@ GetIntegerDeltaForEvent(NSEvent* aEvent)
     handled = mTextInputHandler->HandleKeyDownEvent(theEvent);
   }
 
-  // We always allow keyboard events to propagate to keyDown: but if they are not
-  // handled we give special Application menu items a chance to act.
+  // We always allow keyboard events to propagate to keyDown: but if they are
+  // not handled we give menu items a chance to act. This allows for handling of
+  // custom shortcuts. Note that existing shortcuts cannot be reassigned yet and
+  // will have been handled by keyDown: before we get here.
+  if (!handled && mGeckoChild) {
+    nsCocoaWindow* widget = mGeckoChild->GetXULWindowWidget();
+    if (widget) {
+      nsMenuBarX* mb = widget->GetMenuBar();
+      if (mb) {
+        // Check if main menu wants to handle the event.
+        handled = mb->PerformKeyEquivalent(theEvent);
+      }
+    }
+  }
   if (!handled && sApplicationMenu) {
-    [sApplicationMenu performKeyEquivalent:theEvent];
+    // Check if application menu wants to handle the event.
+    handled = [sApplicationMenu performKeyEquivalent:theEvent];
   }
 
   NS_OBJC_END_TRY_ABORT_BLOCK;
diff --git a/widget/cocoa/nsMenuBarX.h b/widget/cocoa/nsMenuBarX.h
index f976ce4a665c..ea20b1285709 100644
--- a/widget/cocoa/nsMenuBarX.h
+++ b/widget/cocoa/nsMenuBarX.h
@@ -47,6 +47,7 @@ protected:
 @interface GeckoNSMenu : NSMenu
 {
 }
+- (BOOL)performSuperKeyEquivalent:(NSEvent*)theEvent;
 @end
 
 // Objective-C class used as action target for menu items
@@ -119,6 +120,7 @@ public:
   static void       ResetNativeApplicationMenu();
   void              SetNeedsRebuild();
   void              ApplicationMenuOpened();
+  bool              PerformKeyEquivalent(NSEvent* theEvent);
 
 protected:
   void              ConstructNativeMenus();
diff --git a/widget/cocoa/nsMenuBarX.mm b/widget/cocoa/nsMenuBarX.mm
index e4f8c748f2e5..97fe4c1a7425 100644
--- a/widget/cocoa/nsMenuBarX.mm
+++ b/widget/cocoa/nsMenuBarX.mm
@@ -527,6 +527,11 @@ void nsMenuBarX::ApplicationMenuOpened()
   }
 }
 
+bool nsMenuBarX::PerformKeyEquivalent(NSEvent* theEvent)
+{
+  return [mNativeMenu performSuperKeyEquivalent:theEvent];
+}
+
 // Hide the item in the menu by setting the 'hidden' attribute. Returns it in |outHiddenNode| so
 // the caller can hang onto it if they so choose. It is acceptable to pass nsull
 // for |outHiddenNode| if the caller doesn't care about the hidden node.
@@ -876,6 +881,11 @@ static BOOL gMenuItemsExecuteCommands = YES;
   return NO;
 }
 
+- (BOOL)performSuperKeyEquivalent:(NSEvent*)theEvent
+{
+  return [super performKeyEquivalent:theEvent];
+}
+
 @end
 
 //