Wrong runtime loaded on MonoMac app

Xamarin Studio 4.0.9 OS X 10.8.4

I build a MonoMac based project and select the 3.0.10 runtime. However, when the app runs version 2.10.12 is loaded.

From application output: Loaded assembly: /Library/Frameworks/Mono.framework/Versions/2.10.12/lib/mono/gac/System/4.0.0.0__b77a5c561934e089/System.dll [External]

When I build a console version of my app it runs under 3.0.10 as required. The app uses EntityFramework and perishes on 2.10.12

Thanks

Jonathan