Custom Post Type: Quick Edit changes 'the author' not 'modified author'

I have a custom post type called ‘Notices’.

I create a new notice logged in as ‘User1’ and ‘User1’ is shown as the notice author.

‘User99’ now logs in and uses the ‘Quick Edit’ feature on the notice list screen in the admin back end to change a notice. When they save their changes ‘User99’ is now recorded as the author, and not, as would be correct, the modified author.

This behaviour doesn’t seem to occur for ordinary posts.

Has anyone else noticed this behaviour? Anyone got a fix?