Index: channels/chan_iax2.c
===================================================================
--- channels/chan_iax2.c	(revision 152921)
+++ channels/chan_iax2.c	(working copy)
@@ -1558,12 +1558,21 @@
 
 		/* This will occur on the first response to a message that we initiated,
 		 * such as a PING. */
+		if (dcallno) {
+			ast_mutex_lock(&iaxsl[dcallno]);
+		}
 		if (callno && dcallno && iaxs[dcallno] && !iaxs[dcallno]->peercallno && match(sin, callno, dcallno, iaxs[dcallno], check_dcallno)) {
 			iaxs[dcallno]->peercallno = callno;
 			res = dcallno;
 			store_by_peercallno(iaxs[dcallno]);
+			if (!res || !return_locked) {
+				ast_mutex_unlock(&iaxsl[dcallno]);
+			}
 			return res;
 		}
+		if (dcallno) {
+			ast_mutex_unlock(&iaxsl[dcallno]);
+		}
 
 #ifdef IAX_OLD_FIND
 		/* If we get here, we SHOULD NOT find a call structure for this