Custom EL expression in event handlers disappears on save

Using Nuxeo studio current 2.13 test version:
Go to project settings and set target platform as 5.6 + DM
Save
Go to Automation -> Event handlers
Create an event handler or edit an existing one
In the custom EL expression field, type something, e.g.: currentUser == 'Garcimore'
Save
The custom EL expression field is now empty