diff --git a/channels/chan_iax2.c b/channels/chan_iax2.c
index ce32bbf0fc405a5df40e8028e691457b2fd3bf4a..76abb11a753fe653d153e48070fd303c1a84318b 100644
--- a/channels/chan_iax2.c
+++ b/channels/chan_iax2.c
@@ -1700,7 +1700,7 @@ static void iax2_frame_free(struct iax_frame *fr)
 
 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) {