Exception on EF SaveChanges -> DllNotFoundException: SqlServerSpatial110.dll

On a specific installation I get the following exception on DbContext.SaveChanges.

What I don't understand is why this dll is used, as we're not using MSSQL EF, but a different provider (Sybase EF).

The type initializer for 'ExtentPlaceholderCreator' threw an exception. System.TypeInitializationException: The type initializer for 'ExtentPlaceholderCreator' threw an exception. ---> System.Reflection.TargetInvocationException: Exception has been thrown by the target of an invocation. ---> System.DllNotFoundException: Unable to load DLL 'SqlServerSpatial110.dll': The specified module could not be found. (Exception from HRESULT: 0x8007007E)

On an installation where it works, I've tried to rename the dll > SqlServerSpatial110.dll.bak, to see if I could reproduce the error. It had no effect, so I'm left with

1. How to resolve the issue on the installation where it fails?
2. Why is this exception thrown, as the dll most likely is not being used?