diff --git a/gui-lib/framework/preferences.rkt b/gui-lib/framework/preferences.rkt
index 32c1e762..15180a60 100644
--- a/gui-lib/framework/preferences.rkt
+++ b/gui-lib/framework/preferences.rkt
@@ -71,7 +71,7 @@ the state transitions / contracts are:
 
 ;; pref-callback : (make-pref-callback (union (weak-box (sym tst -> void)) (sym tst -> void)))
 ;; this is used as a wrapped to deal with the problem that different procedures might be eq?.
-(define-struct pref-callback (cb))
+(define-struct pref-callback (cb) #:transparent)
 
 ;; used to detect missing hash entries
 (define none (gensym 'none))