diff --git a/endpoints/api/trigger.py b/endpoints/api/trigger.py
index 5ec5c4b0c..72d1ee7a2 100644
--- a/endpoints/api/trigger.py
+++ b/endpoints/api/trigger.py
@@ -402,12 +402,8 @@ class ActivateBuildTrigger(RepositoryParamResource):
           'description': '(Custom Only) If specified, the ref/SHA1 used to checkout a git repository.'
         },
         'refs': {
-          'type': 'array',
-          'description': '(SCM Only) If specified, the refs to build.'
-        },
-        'branch_name': {
-          'type': 'string',
-          'description': '(SCM Only) If specified, the branch to build.'
+          'type': 'object',
+          'description': '(SCM Only) If specified, the ref to build.'
         }
       },
       'additionalProperties': False
diff --git a/test/test_api_usage.py b/test/test_api_usage.py
index 890bcbc94..eadade1b7 100644
--- a/test/test_api_usage.py
+++ b/test/test_api_usage.py
@@ -2993,7 +2993,7 @@ class TestBuildTriggers(ApiTestCase):
     start_json = self.postJsonResponse(ActivateBuildTrigger,
                                        params=dict(repository=ADMIN_ACCESS_USER + '/simple',
                                                    trigger_uuid=trigger.uuid),
-                                       data=dict(refs=[{'kind': 'branch', 'name': 'foobar'}]),
+                                       data=dict(refs={'kind': 'branch', 'name': 'foobar'}),
                                        expected_code=201)
 
   def test_invalid_robot_account(self):
@@ -3058,7 +3058,7 @@ class TestBuildTriggers(ApiTestCase):
     start_json = self.postJsonResponse(ActivateBuildTrigger,
                                        params=dict(repository=ADMIN_ACCESS_USER + '/simple',
                                                    trigger_uuid=trigger.uuid),
-                                       data=dict(),
+                                       data=dict(refs=dict(kind='branch', name='foobar')),
                                        expected_code=201)
 
     assert 'id' in start_json