Channel form and category= parameter issue

Hello,

I’m trying to asign one channel form to specific category. I’m using the following code:

{exp:channel:form channel="mychannel" return="p/ENTRY_ID" category="45" error_handling="inline" rules:tags="required" use_live_url="no" entry_id="{segment_3}" url_title=""}

45 is my category id.

Form works fine but the entry has no asigned category…

Can anybody give me directions on this issue?

Thank you very much.