自定义ServiceHostFactory从未在Windows Server 2012 R2和IIS 8.5上调用

I have a WCF Service solution (NET 4) with custom ServiceHostFactory that works fine on my developer machine (Windows 8.1 and IIS 8.5) but I can't get it working on Windows Server 2012 and IIS 8.5 for some reason. The WCF service itself works on Server 2012, but the ServiceHostFactory is never called. Is there a particular module that I should install via Add Roles or Features in Server 2012 in order to make it work?I have a WCF Service solution (NET 4) with cust