diff --git a/include/wx/dataobj.h b/include/wx/dataobj.h
index 4a905e44fe..9669d9393a 100644
--- a/include/wx/dataobj.h
+++ b/include/wx/dataobj.h
@@ -203,7 +203,7 @@ public:
         { return FALSE; }
 
     // copy data from buffer to our data
-    virtual bool SetData(size_t len, const void *WXUNUSED(buf))
+    virtual bool SetData(size_t WXUNUSED(len), const void *WXUNUSED(buf))
         { return FALSE; }
 
     // implement base class pure virtuals