Again, this code

#+BEGIN_SRC scheme :session ch1 :exports both
(define (bool-imply a b)
  (if (or (not a) b) #t #f))
#+END_SRC

gives the error

org-babel-scheme-execute-with-geiser: Invalid read syntax: "#"

and this time attempting to use the function

#+BEGIN_SRC scheme :session ch1 :exports both
(bool-imply #t #f)
#+END_SRC

produces no #RESULTS: block, rather, again, the error (in Messages buffer)

org-babel-scheme-execute-with-geiser: Invalid read syntax: "#"

even though this is perfectly healthy code, and it works in the
accompanying "ch1" REPL. Any ideas what's happening?