diff --git a/implementations/racket/preserves/preserves/read-text.rkt b/implementations/racket/preserves/preserves/read-text.rkt
index 37043b3..9090789 100644
--- a/implementations/racket/preserves/preserves/read-text.rkt
+++ b/implementations/racket/preserves/preserves/read-text.rkt
@@ -287,10 +287,12 @@
     (define ch (next-char))
     (cond [(eqv? ch #\])
            (base64-decode (string->bytes/latin-1 (list->string (reverse acc))))]
+          [(char=? ch #\-) (read-base64-binary (cons #\+ acc))]
+          [(char=? ch #\_) (read-base64-binary (cons #\/ acc))]
           [(or (and (char>=? ch #\A) (char<=? ch #\Z))
                (and (char>=? ch #\a) (char<=? ch #\z))
                (and (char>=? ch #\0) (char<=? ch #\9))
-               (memv ch '(#\+ #\/ #\- #\_ #\=)))
+               (memv ch '(#\+ #\/ #\=)))
            (read-base64-binary (cons ch acc))]
           [else
            (parse-error "Invalid base64 character")]))