diff --git a/widget/src/cocoa/nsChildView.mm b/widget/src/cocoa/nsChildView.mm
index 06416b05872..5a74cee7071 100644
--- a/widget/src/cocoa/nsChildView.mm
+++ b/widget/src/cocoa/nsChildView.mm
@@ -3979,7 +3979,7 @@ static PRBool IsNormalCharInputtingEvent(const nsKeyEvent& aEvent)
                                kbType, 0, &deadKeyState, 1, &len, chars);
         if (noErr == err && len > 0)
           shiftedCmdChar = chars[0];
-      } else if (handle = (char**)::GetScriptManagerVariable(smKCHRCache)) {
+      } else if ((handle = (char**)::GetScriptManagerVariable(smKCHRCache))) {
         UInt32 state = 0;
         UInt32 keyCode = [aKeyEvent keyCode];
         unshiftedChar = ::KeyTranslate(handle, keyCode, &state) & charCodeMask;
@@ -4851,10 +4851,22 @@ static BOOL keyUpAlreadySentKeyDown = NO;
 
   // Perform native menu UI feedback even if we stop the event from propagating to it normally.
   // Recall that the menu system won't actually execute any commands for keyboard command invocations.
-  // By checking the class for the main menu we ensure that we don't do any of this for embedders.
+  //
+  // If this is a plugin, we do actually perform the action on keyboard commands. See bug 428047.
+  // If the action on plugins here changes the first responder, don't continue.
   NSMenu* mainMenu = [NSApp mainMenu];
-  if ([mainMenu isKindOfClass:[GeckoNSMenu class]])
-    [(GeckoNSMenu*)mainMenu performMenuUserInterfaceEffectsForEvent:theEvent];
+  if (mIsPluginView) {
+    if ([mainMenu isKindOfClass:[GeckoNSMenu class]])
+      [(GeckoNSMenu*)mainMenu actOnKeyEquivalent:theEvent];
+    else
+      [mainMenu performKeyEquivalent:theEvent];
+    if ([[self window] firstResponder] != self)
+      return YES;
+  }
+  else {
+    if ([mainMenu isKindOfClass:[GeckoNSMenu class]])
+      [(GeckoNSMenu*)mainMenu performMenuUserInterfaceEffectsForEvent:theEvent];
+  }
 
   // don't handle this if certain modifiers are down - those should
   // be sent as normal key up/down events and cocoa will do so automatically
diff --git a/widget/src/cocoa/nsMenuBarX.h b/widget/src/cocoa/nsMenuBarX.h
index ead4be0bbb2..c2cffe0fff5 100644
--- a/widget/src/cocoa/nsMenuBarX.h
+++ b/widget/src/cocoa/nsMenuBarX.h
@@ -77,6 +77,7 @@ namespace MenuHelpersX
 {
 }
 - (BOOL)performKeyEquivalent:(NSEvent *)theEvent;
+- (void)actOnKeyEquivalent:(NSEvent *)theEvent;
 - (void)performMenuUserInterfaceEffectsForEvent:(NSEvent*)theEvent;
 @end
 
diff --git a/widget/src/cocoa/nsMenuBarX.mm b/widget/src/cocoa/nsMenuBarX.mm
index 673b5604c5d..489a3ce9b32 100644
--- a/widget/src/cocoa/nsMenuBarX.mm
+++ b/widget/src/cocoa/nsMenuBarX.mm
@@ -949,8 +949,10 @@ NSMenuItem* MenuHelpersX::GetStandardEditMenuItem()
 // is nil, it is not on the stack. The non-nil value is the object that put it
 // on the stack first.
 static GeckoNSMenu* gPerformKeyEquivOnStack = nil;
-// When this variable is set to YES, don't do special command processing.
-static BOOL gMenuEffectsOnly = NO;
+// If this is YES, act on key equivs.
+static BOOL gActOnKeyEquiv = NO;
+// When this variable is set to NO, don't do special command processing.
+static BOOL gActOnSpecialCommands = YES;
 
 @implementation GeckoNSMenu
 
@@ -976,11 +978,19 @@ static BOOL gMenuEffectsOnly = NO;
 }
 
 
+-(void)actOnKeyEquivalent:(NSEvent *)theEvent
+{
+  gActOnKeyEquiv = YES;
+  [self performKeyEquivalent:theEvent];
+  gActOnKeyEquiv = NO;
+}
+
+
 - (void)performMenuUserInterfaceEffectsForEvent:(NSEvent*)theEvent
 {
-  gMenuEffectsOnly = YES;
+  gActOnSpecialCommands = NO;
   [self performKeyEquivalent:theEvent];
-  gMenuEffectsOnly = NO;
+  gActOnSpecialCommands = YES;
 }
 
 @end
@@ -1006,7 +1016,7 @@ static BOOL gMenuEffectsOnly = NO;
   // We want to avoid processing app-global commands when we are asked to
   // perform native menu effects only. This avoids sending events twice,
   // which can lead to major problems.
-  if (!gMenuEffectsOnly) {
+  if (gActOnSpecialCommands) {
     // Do special processing if this is for an app-global command.
     if (tag == eCommand_ID_About) {
       nsIContent* mostSpecificContent = sAboutItemContent;
@@ -1042,7 +1052,7 @@ static BOOL gMenuEffectsOnly = NO;
   // is no main window then the hidden window menu bar is up, even
   // if that isn't true for some reason we better play it safe if
   // there is no main window.
-  if (gPerformKeyEquivOnStack && [NSApp mainWindow])
+  if (gPerformKeyEquivOnStack && !gActOnKeyEquiv && [NSApp mainWindow])
     return;
 
   // given the commandID, look it up in our hashtable and dispatch to