diff --git a/collects/mzlib/pregexp.rkt b/collects/mzlib/pregexp.rkt
index fe41060..5d2c494 100644
--- a/collects/mzlib/pregexp.rkt
+++ b/collects/mzlib/pregexp.rkt
@@ -1,4 +1,4 @@
-;pregexp.ss
+;; pregexp.rkt
 ;; Originally:
 ;;   ;Portable regular expressions for Scheme
 ;;   ;Dorai Sitaram
diff --git a/collects/mzlib/private/sigmatch.rkt b/collects/mzlib/private/sigmatch.rkt
index 84d0fc4..2122e79 100644
--- a/collects/mzlib/private/sigmatch.rkt
+++ b/collects/mzlib/private/sigmatch.rkt
@@ -1,7 +1,6 @@
-
 (module sigmatch mzscheme
 
-  (require "../unit200.ss")
+  (require "../unit200.rkt")
 
   (define (hash-sig src-sig table)
     (and (pair? src-sig)
diff --git a/collects/mzlib/shared.rkt b/collects/mzlib/shared.rkt
index bb6e262..0582997 100644
--- a/collects/mzlib/shared.rkt
+++ b/collects/mzlib/shared.rkt
@@ -16,5 +16,5 @@
   (lambda (stx)
     (define make-check-cdr #f)
     ;; Include the implementation.
-    ;; See private/shared-body.ss.
+    ;; See private/shared-body.rkt.
     (include "private/shared-body.rkt")))