diff --git a/pitfall/restructure/bitfield.rkt b/pitfall/restructure/bitfield.rkt
index 325692cf..d902c582 100644
--- a/pitfall/restructure/bitfield.rkt
+++ b/pitfall/restructure/bitfield.rkt
@@ -9,34 +9,34 @@ https://github.com/mbutterick/restructure/blob/master/src/Bitfield.coffee
 
 (define-subclass Streamcoder (Bitfield type [flags empty])
           
-  (define/augment (decode stream . args)
-    (for*/fold ([flag-hash (mhash)])
-               ([val (in-value (send type decode stream))]
-                [(flag i) (in-indexed flags)]
-                #:when flag)
-      (hash-set! flag-hash flag (bitwise-bit-set? val i))
-      flag-hash))
+  (define/augment (decode stream . _)
+    (define flag-hash (mhasheq))
+    (for* ([val (in-value (send type decode stream))]
+           [(flag i) (in-indexed flags)]
+           #:when flag)
+      (hash-set! flag-hash (if (symbol? flag) flag (string->symbol "~a" flag)) (bitwise-bit-set? val i)))
+    flag-hash)
 
-  (define/override (size . args) (send type size))
+  (define/override (size . _) (send type size))
 
   (define/augment (encode stream flag-hash [ctx #f])
-    (define bitfield-int (for/sum ([(flag i) (in-indexed flags)]
-                                   #:when (and flag (hash-ref flag-hash flag)))
-                           (expt 2 i)))
-    (send type encode stream bitfield-int)))
+    (define bitfield-integer (for/sum ([(flag i) (in-indexed flags)]
+                                       #:when (and flag (ref flag-hash flag)))
+                               (arithmetic-shift 1 i)))
+    (send type encode stream bitfield-integer)))
 
 
 (test-module
  (require "number.rkt" "stream.rkt")
  (define bfer (+Bitfield uint16be '(bold italic underline #f shadow condensed extended)))
  (define bf (send bfer decode (+DecodeStream #"\0\25")))
- (check-equal? (length (hash-keys bf)) 6) ; omits #f flag
- (check-true (hash-ref bf 'bold))
- (check-true (hash-ref bf 'underline))
- (check-true (hash-ref bf 'shadow))
- (check-false (hash-ref bf 'italic))
- (check-false (hash-ref bf 'condensed))
- (check-false (hash-ref bf 'extended))
+ (check-equal? (length (ref-keys bf)) 6) ; omits #f flag
+ (check-true (ref bf 'bold))
+ (check-true (ref bf 'underline))
+ (check-true (ref bf 'shadow))
+ (check-false (ref bf 'italic))
+ (check-false (ref bf 'condensed))
+ (check-false (ref bf 'extended))
 
  (define os (+EncodeStream))
  (send bfer encode os bf)