diff --git a/channels/chan_iax2.c b/channels/chan_iax2.c
index 7d321f45db..ac58c7703d 100644
--- a/channels/chan_iax2.c
+++ b/channels/chan_iax2.c
@@ -1507,7 +1507,7 @@ retry:
 
 static int scheduled_destroy(const void *vid)
 {
-	short callno = PTR_TO_CALLNO(vid);
+	unsigned short callno = PTR_TO_CALLNO(vid);
 	ast_mutex_lock(&iaxsl[callno]);
 	if (iaxs[callno]) {
 		if (option_debug) {