The selected type is not visible and cannot be run by Pex

I'm running Pex 1.4.40602.0. When I try to run Pex on an internal" type I get a "The selected type is not visible and cannot be run by Pex." error dialog. I have tried to place the following commands in my Assembly.cs file, but all to no avail:

[assembly: InternalsVisibleTo("Groucho.Generic.Tests")]
[assembly: InternalsVisibleTo("Groucho.Ge开发者_如何学Pythonneric.Moles")]
[assembly: InternalsVisibleTo("Groucho.Generic.Explorables")]

Any help in this regard would be greatly appreciated....