DispatchProxy seems to have a bug (from my point of view at least).

Here's a dotnetfiddle to illustrate my point:
https://dotnetfiddle.net/Lu1iSN

The method with this signature cannot be proxied and throws an exception:
IGenericHandler GetHandler(T input) where T : GenericBase
Unhandled exception. System.TypeLoadException: GenericArguments[0], 'T', on 'IGenericHandler`1[T]' violates the constraint of type parameter 'T'.
at generatedProxy_1.GetHandler[T]
at Program.Main()

Is it a bug/limitation or am I doing something wrong?
Thanks