diff --git a/openbsc/src/libtrau/rtp_proxy.c b/openbsc/src/libtrau/rtp_proxy.c
index 9251dec..122daf2 100644
--- a/openbsc/src/libtrau/rtp_proxy.c
+++ b/openbsc/src/libtrau/rtp_proxy.c
@@ -196,6 +196,7 @@
 		}
 		break;
 	case RTP_PT_AMR:
+		msg_type = GSM_TCH_FRAME_AMR;
 		break;
 	default:
 		DEBUGPC(DLMUX, "received RTP frame with unknown payload "