diff --git a/gst/rtpmanager/gstrtpdtmfmux.h b/gst/rtpmanager/gstrtpdtmfmux.h
index 69704f2082..866704c79f 100644
--- a/gst/rtpmanager/gstrtpdtmfmux.h
+++ b/gst/rtpmanager/gstrtpdtmfmux.h
@@ -49,6 +49,7 @@ struct _GstRTPDTMFMux
 {
   GstRTPMux mux;
 
+  /* Protected by object lock */
   /* our special pad */
   GstPad *special_pad;
 };