Steps:

1. Add the Attachment field to the screen used for the Close Issue transition.
2. Go to an issue
3. workflow > closed
4. add an attachment in the close issue screen
5. close the issue
6. check the issue for the attachment

Actual result:
The attachment is not there, the issue has to be reopened to get the attachment attached.

Expected result:
The attachment should have been added to the issue when closing it.