diff --git a/oml/websocket.py b/oml/websocket.py
index 3740994..e12544e 100644
--- a/oml/websocket.py
+++ b/oml/websocket.py
@@ -22,7 +22,7 @@ class Handler(WebSocketHandler):
             origin in (
                 'http://127.0.0.1:9841',
                 'http://127.0.0.1:9842',
-                'file:///',
+                'file://',
                 'null'
             )