Setup Wizard Step 4 (Email Notification): Clicking "Test Connection" instantly leads back to Step 2

Steps to reproduce:

• Install JIRA (5.0 beta 3 - build 706)
• Run Setup Wizard
• Step 4: Select "Email Notification:" enable
• fill in valid details (a gmail account in this case)
• click "Test Connection"

expected Result:

Testing the mail server connection ...

result instead:

Setup wizard instantly jumps back to Step 2 with no / default values filled in the form

Experienced during two completely different fresh installs on two different computers.

I assume attaching log files etc. doesn't make much sense in this case. And I'll rather not reproduce it since that would require yet another new installation ...