diff --git a/miniwin/miniwin/src/miniwin_ddsurface.cpp b/miniwin/miniwin/src/miniwin_ddsurface.cpp
index d2a44afd..e4461d2a 100644
--- a/miniwin/miniwin/src/miniwin_ddsurface.cpp
+++ b/miniwin/miniwin/src/miniwin_ddsurface.cpp
@@ -2,6 +2,8 @@
 #include "miniwin_ddsurface_p.h"
 #include "miniwin_p.h"
 
+#include <assert.h>
+
 DirectDrawSurfaceImpl::DirectDrawSurfaceImpl()
 {
 }