diff --git a/channels/chan_sip.c b/channels/chan_sip.c
index 0a53303f07..d1e0a2b16a 100644
--- a/channels/chan_sip.c
+++ b/channels/chan_sip.c
@@ -4934,7 +4934,7 @@ static void initreqprep(struct sip_request *req, struct sip_pvt *p, int sipmetho
 		l = CALLERID_UNKNOWN;
 		n = l;
 	}
-	if (!l)
+	if (ast_strlen_zero(l))
 		l = default_callerid;
 	if (ast_strlen_zero(n))
 		n = l;