The Bug Number field is always blank. Eg

Joe has assigned a Bug to Jean.

Bug Number: <------- blank
Subject: New Ticket
Type: Defect
Priority: Urgent

All the other fields are filled in, as is Bug Number on (subsequent) notifications for Bug *updates* (as opposed to the initial *create*).

In both 4.5 and 5.2.

Is this a configuration issue or should I log a bug ( in the Bug Module )?