diff --git a/endpoints/api/trigger.py b/endpoints/api/trigger.py
index 3dec076b6..95328818d 100644
--- a/endpoints/api/trigger.py
+++ b/endpoints/api/trigger.py
@@ -404,7 +404,7 @@ class ActivateBuildTrigger(RepositoryParamResource):
           'description': '(Custom Only) If specified, the ref/SHA1 used to checkout a git repository.'
         },
         'refs': {
-          'type': 'object',
+          'type': ['object',  'null'],
           'description': '(SCM Only) If specified, the ref to build.'
         }
       },
diff --git a/static/directives/manual-trigger-build-dialog.html b/static/directives/manual-trigger-build-dialog.html
index 56f59ea14..8a8b8ee9e 100644
--- a/static/directives/manual-trigger-build-dialog.html
+++ b/static/directives/manual-trigger-build-dialog.html
@@ -26,7 +26,8 @@
                            icon-key="kind"
                            icon-map="field.iconMap"
                            items="fieldOptions[field.name]"
-                           ng-show="fieldOptions[field.name]"></div>
+                           ng-show="fieldOptions[field.name]"
+                           clear-value="counter"></div>
                     </div>
 
                     <!-- Option -->
diff --git a/static/js/directives/ui/manual-trigger-build-dialog.js b/static/js/directives/ui/manual-trigger-build-dialog.js
index a0f09cae2..80e1c631a 100644
--- a/static/js/directives/ui/manual-trigger-build-dialog.js
+++ b/static/js/directives/ui/manual-trigger-build-dialog.js
@@ -57,6 +57,8 @@ angular.module('quay').directive('manualTriggerBuildDialog', function () {
               $scope.fieldOptions[parameter['name']] = resp['values'];
             });
           }
+
+          delete $scope.parameters[parameter['name']];
         }
 
         $scope.runParameters = parameters;
diff --git a/test/test_api_usage.py b/test/test_api_usage.py
index eead6487f..0291fba4c 100644
--- a/test/test_api_usage.py
+++ b/test/test_api_usage.py
@@ -4059,11 +4059,18 @@ class TestBuildTriggers(ApiTestCase):
     self.assertEquals('bar', py_json.loads(build_obj.job_config)['trigger_metadata']['foo'])
 
     # Start another manual build, with a ref.
-    start_json = self.postJsonResponse(ActivateBuildTrigger,
-                                       params=dict(repository=ADMIN_ACCESS_USER + '/simple',
-                                                   trigger_uuid=trigger.uuid),
-                                       data=dict(refs={'kind': 'branch', 'name': 'foobar'}),
-                                       expected_code=201)
+    self.postJsonResponse(ActivateBuildTrigger,
+                          params=dict(repository=ADMIN_ACCESS_USER + '/simple',
+                                      trigger_uuid=trigger.uuid),
+                          data=dict(refs={'kind': 'branch', 'name': 'foobar'}),
+                          expected_code=201)
+
+    # Start another manual build with a null ref.
+    self.postJsonResponse(ActivateBuildTrigger,
+                          params=dict(repository=ADMIN_ACCESS_USER + '/simple',
+                                      trigger_uuid=trigger.uuid),
+                          data=dict(refs=None),
+                          expected_code=201)
 
   def test_invalid_robot_account(self):
     self.login(ADMIN_ACCESS_USER)