diff --git a/tornado/gen.py b/tornado/gen.py
index 46c726ee..b9d0584b 100644
--- a/tornado/gen.py
+++ b/tornado/gen.py
@@ -23,7 +23,7 @@ could be written with ``gen`` as::
         @gen.engine
         def get(self):
             http_client = AsyncHTTPClient()
-            response = yield gen.Task(http_client.fetch("http://example.com"))
+            response = yield gen.Task(http_client.fetch, "http://example.com")
             do_something_with_response(response)
             self.render("template.html")