gnus-summary-refer-parent-article doesn't work

[Random832]

If I press ^ on an article whose parent does exist on the server but not
in the summary buffer I expected it to fetch the parent from the
server. Instead I just get "Couldn't fetch article <Message-ID>", which
makes the key essentially useless since if it only works for articles
whose parent is in the summary list I can simply use P to select it.

Does anyone know how to make this work? Does this depend on server
support for some feature?