BC30554: masterpage is ambiguous

I did not get this error on my dev machine. I did not get this compilation error in the staging site. I got this error in the produciton site.

Resolution: There was another file called masterpage2.aspx that was using the same namespace masterpage. It looked like a test file or for some reason a blank masterpage file was renamed this. Removed the masterpage2.aspx file , did a build and it worked fine.