diff --git a/apiclient/http.py b/apiclient/http.py
index e84b190..d091a86 100644
--- a/apiclient/http.py
+++ b/apiclient/http.py
@@ -828,8 +828,10 @@
 
     Args:
       callback: callable, A callback to be called for each response, of the
-        form callback(id, response). The first parameter is the request id, and
-        the second is the deserialized response object.
+        form callback(id, response, exception). The first parameter is the
+        request id, and the second is the deserialized response object. The
+        third is an apiclient.errors.HttpError exception object if an HTTP error
+        occurred while processing the request, or None if no error occurred.
       batch_uri: string, URI to send batch requests to.
     """
     if batch_uri is None:
@@ -1030,8 +1032,10 @@
     Args:
       request: HttpRequest, Request to add to the batch.
       callback: callable, A callback to be called for this response, of the
-        form callback(id, response). The first parameter is the request id, and
-        the second is the deserialized response object.
+        form callback(id, response, exception). The first parameter is the
+        request id, and the second is the deserialized response object. The
+        third is an apiclient.errors.HttpError exception object if an HTTP error
+        occurred while processing the request, or None if no errors occurred.
       request_id: string, A unique id for the request. The id will be passed to
         the callback with the response.
 
diff --git a/tests/test_oauth2client_appengine.py b/tests/test_oauth2client_appengine.py
index a11c5e9..edc5996 100644
--- a/tests/test_oauth2client_appengine.py
+++ b/tests/test_oauth2client_appengine.py
@@ -51,8 +51,8 @@
 from google.appengine.runtime import apiproxy_errors
 from oauth2client.anyjson import simplejson
 from oauth2client.appengine import AppAssertionCredentials
-from oauth2client.appengine import FlowProperty
 from oauth2client.appengine import CredentialsModel
+from oauth2client.appengine import FlowProperty
 from oauth2client.appengine import OAuth2Decorator
 from oauth2client.appengine import OAuth2Handler
 from oauth2client.appengine import StorageByKeyName
@@ -64,6 +64,7 @@
 from oauth2client.client import flow_from_clientsecrets
 from webtest import TestApp
 
+
 DATA_DIR = os.path.join(os.path.dirname(__file__), 'data')