diff --git a/googleapiclient/discovery.py b/googleapiclient/discovery.py
index 3359593..771d9fc 100644
--- a/googleapiclient/discovery.py
+++ b/googleapiclient/discovery.py
@@ -333,6 +333,8 @@
 
   if isinstance(service, six.string_types):
     service = json.loads(service)
+  elif isinstance(service, six.binary_type):
+    service = json.loads(service.decode('utf-8'))
 
   if  'rootUrl' not in service and (isinstance(http, (HttpMock,
                                                       HttpMockSequence))):