diff --git a/src/or/directory.c b/src/or/directory.c
index 66381bab9a..974e92583d 100644
--- a/src/or/directory.c
+++ b/src/or/directory.c
@@ -1361,7 +1361,7 @@ write_http_status_line(dir_connection_t *conn, int status,
 {
   char buf[256];
   if (tor_snprintf(buf, sizeof(buf), "HTTP/1.0 %d %s\r\n\r\n",
-      status, reason_phrase) < 0) {
+                   status, reason_phrase ? reason_phrase : "OK") < 0) {
     log_warn(LD_BUG,"Bug: status line too long.");
     return;
   }