Xcode-style control-command-left/right for back/forward -- system alert sound

Since you really need to use Xcode and AppCode together, I'm trying to sanitize some of the keyboard shortcut differences. For some reason, when I bind 'control-command-left' to 'Go To -> Back', it actually does go back but I also hear the OS 'bloop' alert sound...like I just did something wrong. Same goes for 'control-command-left'.

Xcode uses these keybindings without a system alert sound so wtf am I doing wrong? I looked in 'System Preferences -> Keyboard -> Keyboard Shortcuts' for a system binding, but found nothing. Would love to get this cleaned up if anyone has a suggestions.

Thanks