Off by one error.
diff --git a/util.c b/util.c
index 2fb8667..fe9501c 100644
--- a/util.c
+++ b/util.c
@@ -832,7 +832,7 @@ bool extract_sockaddr(struct pool *pool, char *url)
sprintf(url_address, "%.*s", url_len, url_begin);
if (port_len)
- snprintf(port, 5, "%.*s", port_len, port_start);
+ snprintf(port, 6, "%.*s", port_len, port_start);
else
strcpy(port, "80");