[racket] "#%app: unbound identifier" error in DrRacket 6.1.1.4?

Is it just me, or is DrRacket (6.1.1.4, built from the current repo) frequently popping an error like this:

unsaved editor:3:0: #%app: unbound identifier; also, no #%app syntax transformer is bound at: #%app in: (#%app call-with-values (lambda () (quote 42)) print-values)

Seems to be endemic to:
+ unsaved source files.
+ source files with a (module+ main ...).
+ source files with rackunit tests.

The error doesn't prevent the file from running normally.