directx compilation problems

directx compilation problem with MFC:
error LNK2019: unresolved external symbol "int __stdcall lstrlenWInternal(wchar_t const *)" (?lstrlenWInternal@@YGHPB_W@Z) referenced in function "public: ....

Solution:
The definition of lstrlenW is in , included by , i.e. DirectShow (DirectX 9.0 SDK).
Putting #undef lstrlenW after the include solves the problem.