x86 DLL Works But Not x64 DLL

I'm trying to include System.Data.SQLite with my project which is coded in C# and uses .NET Framework v4. I'm a little confused... I'm running Windows 8.1 x64 and the platform target for the project is set to Any CPU. If I include the x64 version of System.Data.SQLite.dll then I get an error saying The type or namespace name 'SQLite' does not exist in the namespace 'System.Data' (are you missing an assembly reference?). However, if I include the x86 version of System.Data.SQLite.dll then it compiles fine. Shouldn't it be the other way around (shouldn't the x86 version not compile)? Since the x86 version works, then can I include just the x86 version with the compiled project? If I need to include both the x86 and x64 version of System.Data.SQLite.dll (as well as SQLite.Interop.dll) then how might I go about doing that? I should also note the version of System.Data.SQLite is v1.0.94.0 (and is for .NET Framework 4).