diff --git a/gcloud/datastore/connection.py b/gcloud/datastore/connection.py
index 52f269141b69..9642be52afc1 100644
--- a/gcloud/datastore/connection.py
+++ b/gcloud/datastore/connection.py
@@ -559,7 +559,7 @@ def _set_read_options(self, request, eventual):
         if eventual:
             opts.read_consistency = datastore_pb.ReadOptions.EVENTUAL
         elif transaction:
-            opts.transaction = transaction
+            opts.transaction = transaction.id()
 
 
 def _copy_deferred_keys(lookup_request, lookup_response):
diff --git a/gcloud/datastore/test_connection.py b/gcloud/datastore/test_connection.py
index ba68138bd1b8..5a5e8e085bbc 100644
--- a/gcloud/datastore/test_connection.py
+++ b/gcloud/datastore/test_connection.py
@@ -268,7 +268,7 @@ def test_lookup_single_key_empty_response_w_eventual_and_transaction(self):
         TRANSACTION = 'TRANSACTION'
         key_pb = Key(path=[{'kind': 'Kind', 'id': 1234}]).to_protobuf()
         conn = self._makeOne()
-        conn.transaction(TRANSACTION)
+        conn.transaction(Transaction(TRANSACTION))
         self.assertRaises(
             ValueError, conn.lookup, DATASET_ID, key_pb, eventual=True)
 
@@ -281,7 +281,7 @@ def test_lookup_single_key_empty_response_w_transaction(self):
         key_pb = Key(path=[{'kind': 'Kind', 'id': 1234}]).to_protobuf()
         rsp_pb = datastore_pb.LookupResponse()
         conn = self._makeOne()
-        conn.transaction(TRANSACTION)
+        conn.transaction(Transaction(TRANSACTION))
         URI = '/'.join([
             conn.API_BASE_URL,
             'datastore',
@@ -569,7 +569,7 @@ def test_run_query_wo_eventual_w_transaction(self):
         rsp_pb.batch.more_results = no_more
         rsp_pb.batch.entity_result_type = datastore_pb.EntityResult.FULL
         conn = self._makeOne()
-        conn.transaction(TRANSACTION)
+        conn.transaction(Transaction(TRANSACTION))
         URI = '/'.join([
             conn.API_BASE_URL,
             'datastore',
@@ -610,7 +610,7 @@ def test_run_query_w_eventual_and_transaction(self):
         rsp_pb.batch.more_results = no_more
         rsp_pb.batch.entity_result_type = datastore_pb.EntityResult.FULL
         conn = self._makeOne()
-        conn.transaction(TRANSACTION)
+        conn.transaction(Transaction(TRANSACTION))
         self.assertRaises(
             ValueError, conn.run_query, DATASET_ID, q_pb, eventual=True)
 
@@ -1174,3 +1174,12 @@ def request(self, **kw):
         self._called_with.append(kw)
         result, self._responses = self._responses[0], self._responses[1:]
         return result
+
+
+class Transaction(object):
+
+    def __init__(self, id):
+        self._id = id
+
+    def id(self):
+        return self._id