diff --git a/collects/typed-scheme/private/free-variance.ss b/collects/typed-scheme/private/free-variance.ss
index db9cb4f8..8d476558 100644
--- a/collects/typed-scheme/private/free-variance.ss
+++ b/collects/typed-scheme/private/free-variance.ss
@@ -27,8 +27,8 @@
 (define var-table (make-weak-hasheq))
 ;; maps Type to List[Cons[Symbol,Variance]]
 
-(define (free-idxs* t) (hash-ref index-table t (lambda _ (error "type not in index-table" (syntax-e t)))))
-(define (free-vars* t) (hash-ref var-table t (lambda _ (error "type not in var-table" (syntax-e t)))))
+(define (free-idxs* t) (hash-ref index-table t (lambda _ (int-err "type ~a not in index-table" (syntax-e t)))))
+(define (free-vars* t) (hash-ref var-table t (lambda _ (int-err "type ~a not in var-table" (syntax-e t)))))
 
 
 (define empty-hash-table (make-immutable-hasheq null))
diff --git a/collects/typed-scheme/private/parse-type.ss b/collects/typed-scheme/private/parse-type.ss
index 2b92c493..0885e9c8 100644
--- a/collects/typed-scheme/private/parse-type.ss
+++ b/collects/typed-scheme/private/parse-type.ss
@@ -213,7 +213,7 @@
           ;(printf "found a type name ~a~n" #'id)
           (make-Name #'id)]
          [else
-          (tc-error/delayed "unbound type ~a" (syntax-e #'id))
+          (tc-error/delayed "unbound type name ~a" (syntax-e #'id))
           Univ])]
 
       [(All . rest) (eq? (syntax-e #'All) 'All) (tc-error "All: bad syntax")]
diff --git a/collects/typed-scheme/private/tc-utils.ss b/collects/typed-scheme/private/tc-utils.ss
index 3e44382e..132b2206 100644
--- a/collects/typed-scheme/private/tc-utils.ss
+++ b/collects/typed-scheme/private/tc-utils.ss
@@ -75,7 +75,7 @@
 (define (tc-error/delayed msg #:stx [stx* (current-orig-stx)] . rest)
   (let ([stx (locate-stx stx*)])
     (unless (syntax? stx)
-      (error "syntax was not syntax" stx (syntax->datum stx*)))
+      (int-err "erroneous syntax was not a syntax object: ~a ~a" stx (syntax->datum stx*)))
     (if (delay-errors?)
         (set! delayed-errors (cons (make-err (apply format msg rest) (list stx)) delayed-errors))
         (raise-typecheck-error (apply format msg rest) (list stx)))))
diff --git a/collects/typed-scheme/private/type-effect-convenience.ss b/collects/typed-scheme/private/type-effect-convenience.ss
index 06ed3c4b..0eb73bcd 100644
--- a/collects/typed-scheme/private/type-effect-convenience.ss
+++ b/collects/typed-scheme/private/type-effect-convenience.ss
@@ -34,7 +34,7 @@
     [(Latent-Remove-Effect: t) (make-Remove-Effect t v)]
     [(True-Effect:) eff]
     [(False-Effect:) eff]
-    [_ (error 'internal-tc-error "can't add var to effect ~a" eff)]))
+    [_ (int-err "can't add var ~a to effect ~a" v eff)]))
 
 (define-syntax (-> stx)
   (syntax-case* stx (:) (lambda (a b) (eq? (syntax-e a) (syntax-e b)))
diff --git a/collects/typed-scheme/private/type-rep.ss b/collects/typed-scheme/private/type-rep.ss
index c63a2a8f..889d0dd5 100644
--- a/collects/typed-scheme/private/type-rep.ss
+++ b/collects/typed-scheme/private/type-rep.ss
@@ -422,7 +422,7 @@
   (match t
     [(Poly: n scope)
      (unless (= (length names) n)
-       (error "Wrong number of names"))
+       (int-err "Wrong number of names: expected ~a got ~a" n (length names)))
      (instantiate-many (map *F names) scope)]))
 
 ;; the 'smart' constructor
@@ -437,7 +437,7 @@
   (match t
     [(PolyDots: n scope)
      (unless (= (length names) n)
-       (error "Wrong number of names"))
+       (int-err "Wrong number of names: expected ~a got ~a" n (length names)))
      (instantiate-many (map *F names) scope)]))
 
 (print-struct #t)