diff --git a/collects/tests/typed-racket/fail/pr13446.rkt b/collects/tests/typed-racket/fail/pr13446.rkt
new file mode 100644
index 00000000..7cc64811
--- /dev/null
+++ b/collects/tests/typed-racket/fail/pr13446.rkt
@@ -0,0 +1,12 @@
+#;
+(exn-pred #rx"blaming: top-level")
+#lang racket/load
+
+(module a typed/racket
+  (provide p)
+  (: p (Parameterof String Index))
+  (define p (make-parameter 0 string-length)))
+
+(require 'a)
+(p 0)
+
diff --git a/collects/typed-racket/private/type-contract.rkt b/collects/typed-racket/private/type-contract.rkt
index 9f087587..0cdd4435 100644
--- a/collects/typed-racket/private/type-contract.rkt
+++ b/collects/typed-racket/private/type-contract.rkt
@@ -422,7 +422,7 @@
         ;; TODO Is this sound?
 	[(Param: in out) 
 	 (set-impersonator!)
-	 #`(parameter/c #,(t->c out))]
+	 #`(parameter/c #,(t->c in) #,(t->c out))]
         [(Hashtable: k v)
          (when (equal? kind flat-sym) (exit (fail)))
          #`(hash/c #,(t->c k #:kind chaperone-sym) #,(t->c v) #:immutable 'dont-care)]