[racket] Augmenting return key behaviour

I'm trying to augment the behaviour of ‹return› to `tabify-all' each time,
 to urge my [3rd-year] students to use when we find them forgetting to do so
 while they try to understand what they've written.

The following [as is or with the commented-out part instead] prevents the
 Interactions from evaluating after ‹return›: it just moves the caret down.
 What am I missing?

  #lang s-exp framework/keybinding-lang

  (keybinding
   "return"
   (λ (editor event)
     (send (send editor get-keymap) call-function "do-return" editor event #t)
     #;(send editor insert-return)))