diff --git a/channels/chan_iax2.c b/channels/chan_iax2.c
index 174a05a28f308bd5cb3f7614f4c37b6434dc17b3..2260bb1671cdb1db93499c92459e4e3c143dfa65 100644
--- a/channels/chan_iax2.c
+++ b/channels/chan_iax2.c
@@ -1474,13 +1474,13 @@ static struct iax_frame *iaxfrdup2(struct iax_frame *fr)
 #define NEW_ALLOW 	1
 #define NEW_FORCE 	2
 
-static int match(struct sockaddr_in *sin, unsigned short callno, unsigned short dcallno, const struct chan_iax2_pvt *cur, int full_frame)
+static int match(struct sockaddr_in *sin, unsigned short callno, unsigned short dcallno, const struct chan_iax2_pvt *cur, int check_dcallno)
 {
 	if ((cur->addr.sin_addr.s_addr == sin->sin_addr.s_addr) &&
 		(cur->addr.sin_port == sin->sin_port)) {
 		/* This is the main host */
 		if ( (cur->peercallno == 0 || cur->peercallno == callno) &&
-			 (full_frame ? dcallno == cur->callno : 1) ) {
+			 (check_dcallno ? dcallno == cur->callno : 1) ) {
 			/* That's us.  Be sure we keep track of the peer call number */
 			return 1;
 		}
@@ -1592,7 +1592,7 @@ static void remove_by_peercallno(struct chan_iax2_pvt *pvt)
 /*
  * \note Calling this function while holding another pvt lock can cause a deadlock.
  */
-static int __find_callno(unsigned short callno, unsigned short dcallno, struct sockaddr_in *sin, int new, int sockfd, int return_locked, int full_frame)
+static int __find_callno(unsigned short callno, unsigned short dcallno, struct sockaddr_in *sin, int new, int sockfd, int return_locked, int check_dcallno)
 {
 	int res = 0;
 	int x;
@@ -1606,7 +1606,7 @@ static int __find_callno(unsigned short callno, unsigned short dcallno, struct s
 				.callno = dcallno,
 				.peercallno = callno,
 				/* hack!! */
-				.frames_received = full_frame,
+				.frames_received = check_dcallno,
 			};
 
 			memcpy(&tmp_pvt.addr, sin, sizeof(tmp_pvt.addr));
@@ -1626,7 +1626,7 @@ static int __find_callno(unsigned short callno, unsigned short dcallno, struct s
 			ast_mutex_lock(&iaxsl[x]);
 			if (iaxs[x]) {
 				/* Look for an exact match */
-				if (match(sin, callno, dcallno, iaxs[x], full_frame)) {
+				if (match(sin, callno, dcallno, iaxs[x], check_dcallno)) {
 					res = x;
 				}
 			}
@@ -1637,7 +1637,7 @@ static int __find_callno(unsigned short callno, unsigned short dcallno, struct s
 			ast_mutex_lock(&iaxsl[x]);
 			if (iaxs[x]) {
 				/* Look for an exact match */
-				if (match(sin, callno, dcallno, iaxs[x], full_frame)) {
+				if (match(sin, callno, dcallno, iaxs[x], check_dcallno)) {
 					res = x;
 				}
 			}
@@ -7998,8 +7998,10 @@ static int socket_process(struct iax2_thread *thread)
 		f.subclass = 0;
 	}
 
-	if (!fr->callno)
-		fr->callno = find_callno(ntohs(mh->callno) & ~IAX_FLAG_FULL, dcallno, &sin, new, fd, ntohs(mh->callno) & IAX_FLAG_FULL);
+	if (!fr->callno) {
+		fr->callno = find_callno(ntohs(mh->callno) & ~IAX_FLAG_FULL, dcallno, &sin, new, fd, 
+			(ntohs(mh->callno) & IAX_FLAG_FULL) && f.frametype == AST_FRAME_IAX && f.subclass == IAX_COMMAND_ACK);
+	}
 
 	if (fr->callno > 0)
 		ast_mutex_lock(&iaxsl[fr->callno]);