diff --git a/heatclient/common/template_utils.py b/heatclient/common/template_utils.py
index 9e9c85bf..b38710be 100644
--- a/heatclient/common/template_utils.py
+++ b/heatclient/common/template_utils.py
@@ -198,6 +198,9 @@ def deep_update(old, new):
         if isinstance(v, collections.Mapping):
             r = deep_update(old.get(k, {}), v)
             old[k] = r
+        elif v is None and isinstance(old.get(k), collections.Mapping):
+            # Don't override empty data, to work around yaml syntax issue
+            pass
         else:
             old[k] = new[k]
     return old
diff --git a/heatclient/tests/unit/test_template_utils.py b/heatclient/tests/unit/test_template_utils.py
index a48e0b36..01cfa13a 100644
--- a/heatclient/tests/unit/test_template_utils.py
+++ b/heatclient/tests/unit/test_template_utils.py
@@ -448,6 +448,51 @@ class ShellEnvironmentTest(testtools.TestCase):
 
         ])
 
+    @mock.patch('six.moves.urllib.request.urlopen')
+    def test_process_multiple_environments_empty_registry(self, mock_url):
+        # Setup
+        env_file1 = '/home/my/dir/env1.yaml'
+        env_file2 = '/home/my/dir/env2.yaml'
+
+        env1 = b'''
+        resource_registry:
+          "OS::Thingy1": "file:///home/b/a.yaml"
+        '''
+        env2 = b'''
+        resource_registry:
+        '''
+        mock_url.side_effect = [six.BytesIO(env1),
+                                six.BytesIO(self.template_a),
+                                six.BytesIO(self.template_a),
+                                six.BytesIO(env2)]
+
+        # Test
+        env_file_list = []
+        files, env = template_utils.process_multiple_environments_and_files(
+            [env_file1, env_file2], env_list_tracker=env_file_list)
+
+        # Verify
+        expected_env = {
+            'resource_registry': {'OS::Thingy1': 'file:///home/b/a.yaml'}}
+        self.assertEqual(expected_env, env)
+
+        self.assertEqual(self.template_a.decode('utf-8'),
+                         files['file:///home/b/a.yaml'])
+
+        self.assertEqual(['file:///home/my/dir/env1.yaml',
+                          'file:///home/my/dir/env2.yaml'], env_file_list)
+        self.assertIn('file:///home/my/dir/env1.yaml', files)
+        self.assertIn('file:///home/my/dir/env2.yaml', files)
+        self.assertEqual(expected_env,
+                         json.loads(files['file:///home/my/dir/env1.yaml']))
+        mock_url.assert_has_calls([
+            mock.call('file://%s' % env_file1),
+            mock.call('file:///home/b/a.yaml'),
+            mock.call('file:///home/b/a.yaml'),
+            mock.call('file://%s' % env_file2),
+
+        ])
+
     def test_global_files(self):
         url = 'file:///home/b/a.yaml'
         env = '''