Add non-breaking space shortcuts to Redactor

Hello!
I’m see that system settings redactor.shortcutsAdd make help me add shortcut for non-breaking space.
But if I set it to value:
{"shift+space": {"func":"insert.html", "params":[" ","false"]}}
It not insert &nbsp; but insert <span class="redactor-invisible-space"></span>.
Please say, what the problem?