diff --git a/bin/ryu-manager b/bin/ryu-manager
index d1bf1302..fca93291 100755
--- a/bin/ryu-manager
+++ b/bin/ryu-manager
@@ -27,6 +27,7 @@ import sys
 from ryu import log
 log.early_init_log(logging.DEBUG)
 
+from ryu import flags
 from ryu import version
 from ryu import utils
 from ryu.app import wsgi