diff --git a/collects/mzlib/kw.rkt b/collects/mzlib/kw.rkt
index 105cc80..6645627 100644
--- a/collects/mzlib/kw.rkt
+++ b/collects/mzlib/kw.rkt
@@ -331,7 +331,7 @@
                                 #`((if (and in-seen? in-keys?)
                                      #,(if allow-duplicate-keys?
                                          #`seen-keys
-                                         #`(error* 'name "duplicate keyword: ~e"
+                                         #`(error* 'name "duplicate keyword: ~.s"
                                                    (car body*)))
                                      (cons (car body*) seen-keys)))
                                 '()))])
@@ -343,12 +343,12 @@
                           nl
                           #`(if in-keys?
                               #,nl
-                              (error* 'name "unknown keyword: ~e"
+                              (error* 'name "unknown keyword: ~.s"
                                       (car body*)))))]
                  [(not allow-other-keys?)
                   #`(if (memq (car body*) 'keywords)
                       #,nl
-                      (error* 'name "unknown keyword: ~e"
+                      (error* 'name "unknown keyword: ~.s"
                               (car body*)))]
                  [else nl]))]
              [expr
@@ -381,7 +381,7 @@
                       #'next-loop
                       #'(if (pair? (cdr body*))
                           next-loop
-                          (error* 'name "keyword list not balanced: ~e" rest*)))
+                          (error* 'name "keyword list not balanced: ~.s" rest*)))
                   #,(if allow-body?
                       (if (and body (not (identifier? body)))
                         (with-syntax ([name (string->symbol
@@ -395,7 +395,7 @@
                         #'expr)
                       #'(if (null? body*)
                           expr
-                          (error* 'name "expecting a ~s keyword got: ~e"
+                          (error* 'name "expecting a ~s keyword got: ~.s"
                                   'keywords (car body*))))))))))
     ;; ------------------------------------------------------------------------
     ;; generates the loop that turns flags to #t's
@@ -456,7 +456,7 @@
           (syntax/loc stx
             (lambda vars
               (if (and (pair? body) (keyword? (car body)))
-                (error* 'name "unknown keyword: ~e" (car body))
+                (error* 'name "unknown keyword: ~.s" (car body))
                 expr)))))]
      ;; no keys => make a case-lambda for optionals
      [(and (null? keys) (not (or body allow-other-keys?)))
diff --git a/collects/mzlib/runtime-path.rkt b/collects/mzlib/runtime-path.rkt
index e1ec2f8..a8c2891 100644
--- a/collects/mzlib/runtime-path.rkt
+++ b/collects/mzlib/runtime-path.rkt
@@ -85,7 +85,7 @@
                                    (null? (cdr strs)))
                               (list "mzlib")
                               (append (cddr p) (drop-right strs 1)))))]
-                [else (error 'runtime-path "unknown form: ~e" p)])))
+                [else (error 'runtime-path "unknown form: ~.s" p)])))
            paths)))
   
   (define-for-syntax (register-ext-files tag-stx paths)
diff --git a/collects/mzlib/unit.rkt b/collects/mzlib/unit.rkt
index b4438f1..22b3c67 100644
--- a/collects/mzlib/unit.rkt
+++ b/collects/mzlib/unit.rkt
@@ -843,7 +843,7 @@
             (names (apply append nameses))
             (dup (check-duplicate-identifier names)))
        (when dup
-         (raise-stx-err (format "duplicate binding for ~e" (syntax-e dup))))
+         (raise-stx-err (format "duplicate binding for ~.s" (syntax-e dup))))
        (quasisyntax/loc stx
          (provide #,@names))))))
 
@@ -1652,7 +1652,7 @@
             (tmp-bindings (map (λ (s) (map tmarker (map car (car s)))) out-sigs))
             (def-table (make-bound-identifier-mapping)))
        (when dup
-         (raise-stx-err (format "duplicate binding for ~e" (syntax-e dup))))
+         (raise-stx-err (format "duplicate binding for ~.s" (syntax-e dup))))
        (for-each
         (λ (sig new-xs)
           (for-each