diff --git a/dlls/msvideo.dll16/msvideo16.c b/dlls/msvideo.dll16/msvideo16.c
index 93724c9a60f..b729ccc870e 100644
--- a/dlls/msvideo.dll16/msvideo16.c
+++ b/dlls/msvideo.dll16/msvideo16.c
@@ -967,6 +967,7 @@ BOOL WINAPI VIDEO_LibMain(DWORD fdwReason, HINSTANCE hinstDLL, WORD ds,
     case DLL_PROCESS_ATTACH:
         break;
     case DLL_PROCESS_DETACH:
+        DeleteCriticalSection(&msvideo_cs);
         break;
     case DLL_THREAD_ATTACH:
     case DLL_THREAD_DETACH: