Crysis 2 - DX 11 Disabled After Applying The Patch?

I have the steam version of Crysis 2. The 1.9 patch was automaticly updated. After it was updated, I applied the texture and DX 11 patch. It seems the texture patch is fine because I can enable it but the DX 11 is still greyed and disabled even after applying the patch. My GPU is Direct X 11 capable (Ati Radeon 6870). Why is it not working?