diff --git a/supervisor/web.py b/supervisor/web.py
index c68de48b8..1190ab62f 100644
--- a/supervisor/web.py
+++ b/supervisor/web.py
@@ -427,7 +427,7 @@ def render(self):
                     return NOT_DONE_YET
                 if message is not None:
                     server_url = form['SERVER_URL']
-                    location = server_url + '?message=%s' % urllib.quote(
+                    location = server_url + "/" + '?message=%s' % urllib.quote(
                         message)
                     response['headers']['Location'] = location