diff --git a/common.c b/common.c
index 3bbdd78..009d325 100644
--- a/common.c
+++ b/common.c
@@ -1689,6 +1689,8 @@ xssl_get_error (SSL *ssl, int result, const char **error_info)
 static char *
 format_host_port_pair (const char *host, const char *port)
 {
+	if (!host)
+		host = "";
 	// IPv6 addresses mess with the "colon notation"; let's go with RFC 2732
 	if (strchr (host, ':'))
 		return xstrdup_printf ("[%s]:%s", host, port);