diff --git a/channels/chan_unistim.c b/channels/chan_unistim.c
index fcbe8a124a..f8ed7d6701 100644
--- a/channels/chan_unistim.c
+++ b/channels/chan_unistim.c
@@ -2151,9 +2151,9 @@ static void start_rtp(struct unistim_subchannel *sub)
 			buffsend[16] = (htons(sin.sin_port) & 0x00ff);
 			buffsend[20] = (us.sin_port & 0xff00) >> 8;
 			buffsend[19] = (us.sin_port & 0x00ff);
-			buffsend[11] = codec;
 		}
-		buffsend[12] = codec;
+		buffsend[11] = codec; /* rx */
+		buffsend[12] = codec; /* tx */
 		send_client(SIZE_HEADER + sizeof(packet_send_open_audio_stream_tx), buffsend,
 				   sub->parent->parent->session);
 
@@ -2181,9 +2181,9 @@ static void start_rtp(struct unistim_subchannel *sub)
 			buffsend[16] = (htons(sin.sin_port) & 0x00ff);
 			buffsend[20] = (us.sin_port & 0xff00) >> 8;
 			buffsend[19] = (us.sin_port & 0x00ff);
-			buffsend[12] = codec;
 		}
-		buffsend[11] = codec;
+		buffsend[11] = codec; /* rx */
+		buffsend[12] = codec; /* tx */
 		send_client(SIZE_HEADER + sizeof(packet_send_open_audio_stream_rx), buffsend,
 				   sub->parent->parent->session);
 	} else {