diff --git a/include/winbase.h b/include/winbase.h
index 78ed660cc72..39a4a9c9ace 100644
--- a/include/winbase.h
+++ b/include/winbase.h
@@ -2079,6 +2079,7 @@ WINBASEAPI BOOL        WINAPI FreeResource(HGLOBAL);
 WINADVAPI  PVOID       WINAPI FreeSid(PSID);
 WINADVAPI  BOOL        WINAPI GetAce(PACL,DWORD,LPVOID*);
 WINADVAPI  BOOL        WINAPI GetAclInformation(PACL,LPVOID,DWORD,ACL_INFORMATION_CLASS);
+WINBASEAPI DWORD       WINAPI GetActiveProcessorCount(WORD);
 WINBASEAPI HRESULT     WINAPI GetApplicationRestartSettings(HANDLE,WCHAR*,DWORD*,DWORD*);
 WINBASEAPI UINT        WINAPI GetAtomNameA(ATOM,LPSTR,INT);
 WINBASEAPI UINT        WINAPI GetAtomNameW(ATOM,LPWSTR,INT);