Have MasterPage inherit a dll

We have a custom DLL that we need to have our master pager inherit

In previous versions of SP we would just add this:

<%@Master language="C#" Inherits="WPManager.WPEvents,WPManager, Version=1.0.0.0, Culture=neutral, PublicKeyToken=b2f96412512f41df"%>

I have tried adding this in the HTML page our master is associated with but no matter what I try it just give an xml error.. we have tried the SPM tags ... 

Any ideas?

sayitfast