diff --git a/relay32/winmm.spec b/relay32/winmm.spec
index c6d167b64cd..8ba51f8eb05 100644
--- a/relay32/winmm.spec
+++ b/relay32/winmm.spec
@@ -7,7 +7,7 @@ init WINMM_LibMain
   3 stub WINMM_3
   4 stdcall CloseDriver(long long long) CloseDriver
   5 stdcall DefDriverProc(long long long long long) DefDriverProc
-  6 stub DriverCallback
+  6 stdcall DriverCallback(long long long long long long long) DriverCallback
   7 stdcall DrvClose(long long long) CloseDriver
   8 stdcall DrvDefDriverProc(long long long long long) DefDriverProc
   9 stdcall DrvGetModuleHandle(long) GetDriverModuleHandle