bug#49686: Confusing presence of #f in error message

Hello,

At the Guile prompt:

scheme@(guile-user)> (if #t (begin (define var 5) (display var))
While compiling expression:
Syntax error:
unknown file:#f:#f: definition in expression context, where definitions 
are not allowed, in form (define var 5)

The "#f:#f:" part in the error message does not look
expected. This is Guile 3.0.5.130-5a1e7.

Best regards,
Jean Abou Samra