diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index d15f3ddc7ecbad9fff5fb1f241f0f0ee6bee4897..e410cfee44856559232d39a78700f8b9b2694a88 100755
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -7926,7 +7926,7 @@ static int reply_digest(struct sip_pvt *p, struct sip_request *req,
 	ast_copy_string(tmp, get_header(req, header), sizeof(tmp));
 	if (ast_strlen_zero(tmp)) 
 		return -1;
-	if (strstr(tmp, "Digest ") != tmp) {
+	if (strncasecmp(tmp, "Digest ", strlen("Digest "))) {
 		ast_log(LOG_WARNING, "missing Digest.\n");
 		return -1;
 	}