diff --git a/src/libosmo-mgcp/mgcp_msg.c b/src/libosmo-mgcp/mgcp_msg.c
index f732158..648d86b 100644
--- a/src/libosmo-mgcp/mgcp_msg.c
+++ b/src/libosmo-mgcp/mgcp_msg.c
@@ -454,10 +454,10 @@
 	}
 
 	/* Check for over long connection identifiers */
-	if (strlen(conn_id) > MGCP_CONN_ID_MAXLEN) {
+	if (strlen(conn_id) > (MGCP_CONN_ID_MAXLEN-1)) {
 		LOGP(DLMGCP, LOGL_ERROR,
-		     "endpoint:0x%x invalid ConnectionIdentifier (too long) 0x%s\n",
-		     ENDPOINT_NUMBER(endp), conn_id);
+		     "endpoint:0x%x invalid ConnectionIdentifier (too long: %zu > %d) 0x%s\n",
+		     ENDPOINT_NUMBER(endp), strlen(conn_id), MGCP_CONN_ID_MAXLEN-1, conn_id);
 		return 510;
 	}