diff --git a/moto/cloudformation/models.py b/moto/cloudformation/models.py
index 70c15d697..b89d76605 100644
--- a/moto/cloudformation/models.py
+++ b/moto/cloudformation/models.py
@@ -107,7 +107,7 @@ class FakeStack(BaseModel):
     def update(self, template, role_arn=None, parameters=None, tags=None):
         self._add_stack_event("UPDATE_IN_PROGRESS", resource_status_reason="User Initiated")
         self.template = template
-        self.resource_map.update(json.loads(template), parameters)
+        self.resource_map.update(self.template_dict, parameters)
         self.output_map = self._create_output_map()
         self._add_stack_event("UPDATE_COMPLETE")
         self.status = "UPDATE_COMPLETE"