diff --git a/gcloud/datastore/connection.py b/gcloud/datastore/connection.py
index acbaa7f67007..cf56f242d925 100644
--- a/gcloud/datastore/connection.py
+++ b/gcloud/datastore/connection.py
@@ -288,8 +288,6 @@ def begin_transaction(self, project):
         :returns: The serialized transaction that was begun.
         """
         request = _datastore_pb2.BeginTransactionRequest()
-        request.isolation_level = (
-            _datastore_pb2.BeginTransactionRequest.SERIALIZABLE)
         response = self._rpc(project, 'beginTransaction', request,
                              _datastore_pb2.BeginTransactionResponse)
         return response.transaction
diff --git a/gcloud/datastore/test_connection.py b/gcloud/datastore/test_connection.py
index 2df5c34d3f43..bf8df54b3c7f 100644
--- a/gcloud/datastore/test_connection.py
+++ b/gcloud/datastore/test_connection.py
@@ -664,7 +664,6 @@ def test_begin_transaction(self):
         rq_class = datastore_pb2.BeginTransactionRequest
         request = rq_class()
         request.ParseFromString(cw['body'])
-        self.assertEqual(request.isolation_level, rq_class.SERIALIZABLE)
 
     def test_commit_wo_transaction(self):
         from gcloud._testing import _Monkey