--- channels/chan_sip.c	(Asterisk 13.11.2)
+++ channels/chan_sip.c	(working copy)
@@ -18744,6 +18744,8 @@ static void set_peer_nat(const struct si
 			ast_clear_flag(&peer->flags[1], SIP_PAGE2_SYMMETRICRTP);
 		}
 	}
+
+	ast_copy_flags(&peer->flags[0], &p->flags[0], SIP_NAT_RPORT_PRESENT);
 }
 
 /*! \brief Check and see if the requesting UA is likely to be behind a NAT.