TinyMCE dropdown menu item text is unintentionally overlapped by keyboard shortcuts

TinyMCE dropdown menu item text is unintentionally overlapped by keyboard
shortcuts

I'm using TinyMCE to allow my users to edit some HTML in a WYSIWYG manner,
and it works well, however there's one problem.
The dropdown menu item text (i.e. File > New Document) is being overlapped
by its accompanied keyboard shortcut.
Here's a screenshot:

You can see that the Undo, Redo, Cut, Copy, and Paste items are all being
overlapped.
I'm not sure what's causing this. Can anybody help me figure out how to
fix this?
Thanks!