XF 1.4 Change 'forums' to 'forum'?

I just tried that and it didn't work. I opened 'phrases' searched for 'forums', changed it to forum, and it still displays as forums.

Edit: Tried again and got this - Phrase titles must be unique in a language. The specified phrase is already in use.
Nope, I'm changing both, and I get the error above.

There are 2 phases in the list... one is forum, and another is forums.

On the navbar it is still displaying as forums.
Ok, so how do I do it without changing the phrase, so that it just DISPLAYS as "forum" in that one particular place?

Is this something would would be doable with the new navbar options in XF2?