diff --git a/rostests/winetests/mlang/mlang.c b/rostests/winetests/mlang/mlang.c
index 5718b52c08f..80494688cc0 100644
--- a/rostests/winetests/mlang/mlang.c
+++ b/rostests/winetests/mlang/mlang.c
@@ -2092,7 +2092,7 @@ static HRESULT WINAPI stream_Clone(IStream *iface, IStream **stream)
     return E_NOTIMPL;
 }
 
-static IStreamVtbl stream_vtbl =
+static /* const */ IStreamVtbl stream_vtbl =
 {
     stream_QueryInterface,
     stream_AddRef,