After a failed stack update, Heat was ignoring the contents of the new environment when reading backed up resources; that is, those that were set aside while their replacements were being created. In particular, it was not picking up any new resource type aliases. As a consequence, if a new resource was successfully created using a new type alias in the environment before the update failed, further attempts to update the stack failed due to the inability to load a resource with an unknown type alias. With this update, backup resources are now stored with a merged combination of the old and new environments. As a result, after an update failure in this scenario, a subsequent update can now recover the stack.