diff --git a/parser-tools/private-lex/deriv.rkt b/parser-tools/private-lex/deriv.rkt
index 7f597e3..77b7488 100644
--- a/parser-tools/private-lex/deriv.rkt
+++ b/parser-tools/private-lex/deriv.rkt
@@ -263,7 +263,11 @@
                                        (set! new-state? #t)
                                        (state new-re (get-state-number))))]
                    [new-all-states (if new-state? (cons new-state all-states) all-states)])
-              (hash-update! transitions s (λ (v) (cons (cons c new-state) v)) '())
+              (hash-set! transitions 
+                         s
+                         (cons (cons c new-state)
+                               (hash-ref transitions s
+                                         '())))
               (cond
                 [new-state?
                  (loop old-states (cons new-state new-states) new-all-states (cdr cs))]
diff --git a/parser-tools/private-yacc/lr0.rkt b/parser-tools/private-yacc/lr0.rkt
index ce504d6..193cd24 100644
--- a/parser-tools/private-yacc/lr0.rkt
+++ b/parser-tools/private-yacc/lr0.rkt
@@ -59,7 +59,7 @@
 (define (reverse-assoc assoc)
   (define reverse-hash (make-hash))
   (define (hash-table-add! ht k v)
-    (hash-update! ht k (λ (v) (cons v v)) '()))
+    (hash-set! ht k (cons v (hash-ref ht k '()))))
   (for ([trans-key/kernel (in-list assoc)])
        (define tk (car trans-key/kernel))
        (hash-table-add! reverse-hash