diff --git a/samples/ipc/connection.h b/samples/ipc/connection.h
index 18152416d4..81ff6e7b12 100644
--- a/samples/ipc/connection.h
+++ b/samples/ipc/connection.h
@@ -69,7 +69,7 @@ protected:
               break;
         }
 
-        wxLogMessage("%s,%d)", s, size);
+        wxLogMessage("%s,%lu)", s, (unsigned long)size);
     }
 };