Discrepancy between docs and live for deploy-key updates

The API docs specify that a deploy key can be updated by sending a PUT to the key's URL:

https://bitbucket.org/api/1.0/repositories/

/

/deploy-keys/

This worked as documented until a few weeks ago, when attempting to update a deploy key began returning a 400 error with the message "The content of a deploy key cannot be modified."

Is this an intentional change, and if so, can the documentation be updated to reflect it?