diff --git a/dlls/wmvcore/wmvcore.h b/dlls/wmvcore/wmvcore.h
index f4b096313b2..ca06e0a4a6f 100644
--- a/dlls/wmvcore/wmvcore.h
+++ b/dlls/wmvcore/wmvcore.h
@@ -25,9 +25,9 @@
 #include "windef.h"
 #include "winbase.h"
 
-static inline void *heap_alloc(size_t len)
+static inline void* __WINE_ALLOC_SIZE(1) heap_alloc(size_t size)
 {
-    return HeapAlloc(GetProcessHeap(), 0, len);
+    return HeapAlloc(GetProcessHeap(), 0, size);
 }
 
 static inline BOOL heap_free(void *mem)