diff --git a/include/osmocom/mgcp/mgcp_common.h b/include/osmocom/mgcp/mgcp_common.h
index 7684936..7aa5d3f 100644
--- a/include/osmocom/mgcp/mgcp_common.h
+++ b/include/osmocom/mgcp/mgcp_common.h
@@ -76,4 +76,7 @@
 /  (see also RFC3435 section 3.2.1.3) */
 #define MGCP_ENDPOINT_MAXLEN (255*2+1+1)
 
+/* A prefix to denote the virtual trunk (RTP on both ends) */
+#define MGCP_ENDPOINT_PREFIX_VIRTUAL_TRUNK "rtpbridge/"
+
 #endif