diff --git a/heat/engine/service.py b/heat/engine/service.py
index 000ec6759b..67e1c4fa63 100644
--- a/heat/engine/service.py
+++ b/heat/engine/service.py
@@ -835,7 +835,7 @@ class EngineService(service.Service):
         # stack definition.  If PARAM_EXISTING is specified, we merge
         # any environment provided into the existing one and attempt
         # to use the existing stack template, if one is not provided.
-        if args.get(rpc_api.PARAM_EXISTING, None):
+        if args.get(rpc_api.PARAM_EXISTING):
             existing_env = current_stack.env.user_env_as_dict()
             existing_params = existing_env[env_fmt.PARAMETERS]
             clear_params = set(args.get(rpc_api.PARAM_CLEAR_PARAMETERS, []))
@@ -872,12 +872,14 @@ class EngineService(service.Service):
                                   'previous template stored'))
                     msg = _('PATCH update to non-COMPLETE stack')
                     raise exception.NotSupported(feature=msg)
+            tmpl = templatem.Template(new_template, files=new_files,
+                                      env=new_env)
+            for key in list(new_env.params.keys()):
+                if key not in tmpl.param_schemata():
+                    new_env.params.pop(key)
         else:
-            new_env = environment.Environment(params)
-            new_files = files
-            new_template = template
-
-        tmpl = templatem.Template(new_template, files=new_files, env=new_env)
+            tmpl = templatem.Template(template, files=files,
+                                      env=environment.Environment(params))
 
         max_resources = cfg.CONF.max_resources_per_stack
         if max_resources != -1 and len(tmpl[tmpl.RESOURCES]) > max_resources:
diff --git a/heat/tests/engine/service/test_stack_update.py b/heat/tests/engine/service/test_stack_update.py
index e33cd6ce94..766192eb88 100644
--- a/heat/tests/engine/service/test_stack_update.py
+++ b/heat/tests/engine/service/test_stack_update.py
@@ -149,6 +149,7 @@ class ServiceStackUpdateTest(common.HeatTestCase):
         stk.set_stack_user_project_id('1234')
         self.assertEqual({'KeyName': 'test'}, stk.t.env.params)
 
+        t['parameters']['newparam'] = {'type': 'number'}
         with mock.patch('heat.engine.stack.Stack') as mock_stack:
             stk.update = mock.Mock()
             mock_stack.load.return_value = stk
@@ -187,6 +188,7 @@ class ServiceStackUpdateTest(common.HeatTestCase):
         self.assertEqual({'KeyName': 'test', 'removeme': 'foo'},
                          stk.t.env.params)
 
+        t['parameters']['newparam'] = {'type': 'number'}
         with mock.patch('heat.engine.stack.Stack') as mock_stack:
             stk.update = mock.Mock()
             mock_stack.load.return_value = stk
diff --git a/heat_integrationtests/functional/test_template_resource.py b/heat_integrationtests/functional/test_template_resource.py
index 9a3e833694..ebfd73e8a7 100644
--- a/heat_integrationtests/functional/test_template_resource.py
+++ b/heat_integrationtests/functional/test_template_resource.py
@@ -935,3 +935,69 @@ resources:
             stack_identifier,
             self.main_template_update,
             files={'resource.yaml': self.nested_templ_update})
+
+
+class TemplateResourceRemovedParamTest(functional_base.FunctionalTestsBase):
+
+    main_template = '''
+heat_template_version: 2013-05-23
+parameters:
+  value1:
+    type: string
+    default: foo
+resources:
+  my_resource:
+    type: resource.yaml
+    properties:
+       value1: {get_param: value1}
+'''
+    nested_templ = '''
+heat_template_version: 2013-05-23
+parameters:
+  value1:
+    type: string
+    default: foo
+resources:
+  test:
+    type: OS::Heat::TestResource
+    properties:
+      value: {get_param: value1}
+'''
+    main_template_update = '''
+heat_template_version: 2013-05-23
+resources:
+  my_resource:
+    type: resource.yaml
+'''
+    nested_templ_update = '''
+heat_template_version: 2013-05-23
+parameters:
+  value1:
+    type: string
+    default: foo
+  value2:
+    type: string
+    default: bar
+resources:
+  test:
+    type: OS::Heat::TestResource
+    properties:
+      value:
+        str_replace:
+          template: VAL1-VAL2
+          params:
+            VAL1: {get_param: value1}
+            VAL2: {get_param: value2}
+'''
+
+    def test_update(self):
+        stack_identifier = self.stack_create(
+            template=self.main_template,
+            environment={'parameters': {'value1': 'spam'}},
+            files={'resource.yaml': self.nested_templ})
+
+        self.update_stack(
+            stack_identifier,
+            self.main_template_update,
+            environment={'parameter_defaults': {'value2': 'egg'}},
+            files={'resource.yaml': self.nested_templ_update}, existing=True)