*** Bug 1469624 has been marked as a duplicate of this bug. ***
This bug appears to have been reported against 'rawhide' during the Fedora 27 development cycle. Changing version to '27'.
For the record, ksh93's behaviour is the behaviour that will likely be recommended by POSIX in the next major version of the standard: http://www.austingroupbugs.net/view.php?id=51