You have a good point there. Fortunately it can be fixed trivially, by returning the definition of 'ar-gensym to its original form and using 'string->uninterned-symbol instead of 'string->symbol. (I suspect this is what mzscheme 'gensym does anyways.) (define (ar-gensym)
(set! ar-gensym-count (+ ar-gensym-count 1))
(string->uninterned-symbol (string-append "gs" (number->string ar-gensym-count))))