I have added a simple yes no dropdown to the contacts module using the edit custom fields functionality. However when I try to search using this field using "yes" I get those set to yes only, however if I search for no I get those set to yes *and* those set to no.

is this expected behaviour? if so how do I achieve being able to search on one or other value?

I understand that thi sis expected bahaviour for a check box which is why I tried a dropdown.

Can anybody shed any light on it?

(Sugar version 4.2)