在x64位操作系统上从“Any CPU”构建的应用程序反映x86程序集

I have a .Net app that's compiled as "Any CPU". I am running it on a x64 OS so it's running as 64bit. The application loads other assemblies that the user provides. It uses reflection of course to read types from the user provided assembly. Everything works fine if the user assembly is compiled as "Any CPU". But if the assembly is compiled as x86, I get the "this is not a Win32 application" exception at reflection time. It's obviously due to the fact that the host app is running 64bit. I have a .Net app that's compiled as "Any CPU".