Conditional Formatting in Infopath

I have created a very simple form in InfoPath. There is a part where I have a check box called Other, and beneath it, a text box. I set the conditional formatting on the text box to say “If (check box) is blank, hide (text box)”. It does not work with the check box. If I put an option button there instead it works just fine. Does the check box have some strange rules that i don’t know when it comes to conditional formatting?

Thank you!