diff --git a/collects/typed-scheme/env/type-environments.ss b/collects/typed-scheme/env/type-environments.ss
index b62d7d024a..3a0b5679a1 100644
--- a/collects/typed-scheme/env/type-environments.ss
+++ b/collects/typed-scheme/env/type-environments.ss
@@ -20,7 +20,7 @@
          with-dotted-env/extend)
 
 ;; eq? has the type of equal?, and l is an alist (with conses!)
-(define-struct env (eq? l))
+(r:d-s/c env ([eq? (any/c any/c . -> . boolean?)] [l (listof pair?)]))
 
 (define (env-vals e)
   (map cdr (env-l e)))
@@ -45,7 +45,8 @@
 ;; the environment for types of ... variables
 (define dotted-env (make-parameter (make-empty-env free-identifier=?)))
 
-(define (env-map f env)
+(define/contract (env-map f env)
+  ((pair? . -> . pair?) env? . -> . env?)
   (make-env (env-eq? env) (map f (env-l env))))
 
 ;; extend that works on single arguments
diff --git a/collects/typed-scheme/typecheck/tc-envops.ss b/collects/typed-scheme/typecheck/tc-envops.ss
index a7fa27867a..292391ed00 100644
--- a/collects/typed-scheme/typecheck/tc-envops.ss
+++ b/collects/typed-scheme/typecheck/tc-envops.ss
@@ -50,6 +50,6 @@
   (env? (listof Filter/c) . -> . env?)
   (for/fold ([Γ env]) ([f fs])
     (match f
-      [(Bot:) (env-map (lambda (_) (Un)) Γ)]
+      [(Bot:) (env-map (lambda (x) (cons (car x) (Un))) Γ)]
       [(or (TypeFilter: _ _ x) (NotTypeFilter: _ _ x))
        (update-type/lexical (lambda (x t) (update t f)) x Γ)])))