diff --git a/collects/srfi/14/char-set.ss b/collects/srfi/14/char-set.ss
index a5a373bac1..eb9663ccd0 100644
--- a/collects/srfi/14/char-set.ss
+++ b/collects/srfi/14/char-set.ss
@@ -244,10 +244,10 @@
      [(cs . more)
       (fold-set char-set-delete cs more)]))
 
-  (define (char-set-complement cs)
-    (make-char-set
-     (union (complement (char-set-set cs) #x0 #xD7FF)
-	    (complement (char-set-set cs) #xE000 #x10FFFF))))
+   (define (char-set-complement cs)
+     (make-char-set
+      (difference (complement (char-set-set cs) 0 #x10FFFF)
+  	         (make-range #xD800 #xDFFF))))
 
   (define-syntax define-set-op
     (syntax-rules ()
diff --git a/collects/tests/mzscheme/char-set.ss b/collects/tests/mzscheme/char-set.ss
index 0434dbd938..87008e752d 100644
--- a/collects/tests/mzscheme/char-set.ss
+++ b/collects/tests/mzscheme/char-set.ss
@@ -52,7 +52,8 @@
 (test #t char-set-contains? char-set:letter+digit #\A)
 (test #t char-set-contains? char-set:letter+digit #\Z)
 
-(test 90547 char-set-size char-set:letter)
+;; As of Unicode 4.1:
+(test 91395 char-set-size char-set:letter)
 
 (test #t char-set= char-set:letter+digit (char-set-union char-set:letter char-set:digit))
 ;; Slow!:
@@ -108,8 +109,9 @@
 
 ;; Iterating over character sets ----------------------------------------
 
-;; The number 268 comes from "grep Nd UnicodeData.txt | wc -l"
-(test 268 char-set-size char-set:digit)
+;; The number 270 comes from "grep Nd UnicodeData.txt | wc -l"
+;; in Unicode 4.1
+(test 270 char-set-size char-set:digit)
 
 (test #t char-set=
       char-set:digit
@@ -492,4 +494,9 @@
 
 ;; ----------------------------------------
 
+;; PR 8624 --- make sure there's no error:
+(test #t values (string? (char-set->string (char-set-complement char-set:graphic))))
+
+;; ----------------------------------------
+
 (report-errs)