cli v7 cannot add plugin via git+ssh

In previous versions (including 6.5), the following command would work:

cordova plugin add git+ssh://git@github.com/XXX/XXX.git#HASH

This appears to be broken in v7; it results in the following error:

Error: Failed to fetch plugin ssh://git@github.com/XXX/XXX#HASH via registry.
Probably this is either a connection problem, or plugin spec is incorrect.
Check your connection and plugin name/version/URL.
Failed to get absolute path to installed module