diff --git a/include/wx/msw/private.h b/include/wx/msw/private.h
index 31a435f2a4..e3cb8dbc7b 100644
--- a/include/wx/msw/private.h
+++ b/include/wx/msw/private.h
@@ -338,7 +338,8 @@ struct WinStruct : public T
 {
     WinStruct()
     {
-        ::ZeroMemory(this, cbSize = sizeof(T));
+        ::ZeroMemory(this, sizeof(T));
+        cbSize = sizeof(T);
     }
 };