diff --git a/gns3server/web/response.py b/gns3server/web/response.py
index 318b7518..c394d305 100644
--- a/gns3server/web/response.py
+++ b/gns3server/web/response.py
@@ -44,9 +44,9 @@ class Response(aiohttp.web.Response):
         headers['Server'] = "Python/{0[0]}.{0[1]} GNS3/{1}".format(sys.version_info, __version__)
         super().__init__(headers=headers, **kwargs)
 
-    def enable_chunked_encoding():
+    def enable_chunked_encoding(self):
         # Very important: do not send a content length otherwise QT closes the connection (curl can consume the feed)
-        response.content_length = None
+        self.content_length = None
         super().enable_chunked_encoding()
 
     @asyncio.coroutine