diff --git a/collects/tests/typed-racket/succeed/struct-mutable-contract.rkt b/collects/tests/typed-racket/succeed/struct-mutable-contract.rkt
new file mode 100644
index 00000000..ff228fb4
--- /dev/null
+++ b/collects/tests/typed-racket/succeed/struct-mutable-contract.rkt
@@ -0,0 +1,14 @@
+#lang racket/load
+
+(module promise typed/racket/base
+  (require (for-syntax racket/base))
+  (provide MyPromise)
+  (define-struct: (a) MyPromise ([thunk : (-> a)])
+    #:mutable))
+
+(module user racket/base
+  (require 'promise)
+  (MyPromise (lambda () #f)))
+  
+
+(require 'user)
diff --git a/collects/typed-racket/private/type-contract.rkt b/collects/typed-racket/private/type-contract.rkt
index 53312a1c..74cd0334 100644
--- a/collects/typed-racket/private/type-contract.rkt
+++ b/collects/typed-racket/private/type-contract.rkt
@@ -142,9 +142,9 @@
     (let loop ([ty ty] [typed-side (if typed-side 'typed 'untyped)] [structs-seen null] [kind kind])
       (define (t->c t #:seen [structs-seen structs-seen] #:kind [kind kind])
         (loop t typed-side structs-seen kind))
-      (define (t->c/neg t #:seen [structs-seen structs-seen] #:flat [kind kind])
+      (define (t->c/neg t #:seen [structs-seen structs-seen] #:kind [kind kind])
         (loop t (flip-side typed-side) structs-seen kind))
-      (define (t->c/both t #:seen [structs-seen structs-seen] #:flat [kind kind])
+      (define (t->c/both t #:seen [structs-seen structs-seen] #:kind [kind kind])
         (loop t 'both structs-seen kind))
       (define (t->c/fun f #:method [method? #f])
         (match f