diff --git a/collects/srfi/14/char-set.ss b/collects/srfi/14/char-set.ss
index b5fd04d254..30acda81c6 100644
--- a/collects/srfi/14/char-set.ss
+++ b/collects/srfi/14/char-set.ss
@@ -273,14 +273,17 @@
 
   (define char-set-diff+intersection
     (case-lambda
-     [(cs1 cs2)
-      (let-values ([(cs1^cs2 cs1-cs2 cs2-cs1) (split (char-set-set cs1) (char-set-set cs2))])
-	(values (make-char-set cs1-cs2)
-		(make-char-set cs1^cs2)))]
-     [(cs1 cs2 . more)
-      (let-values ([(d i) (char-set-diff+intersection cs1 cs2)])
-	(values (apply char-set-difference d more)
-		(apply char-set-intersection i more)))]))
+      [(cs)
+       (values (char-set-difference cs)
+               (char-set-intersection cs (char-set-union)))]
+      [(cs1 cs2)
+       (let-values ([(cs1^cs2 cs1-cs2 cs2-cs1) (split (char-set-set cs1) (char-set-set cs2))])
+         (values (make-char-set cs1-cs2)
+                 (make-char-set cs1^cs2)))]
+      [(cs1 cs2 . more)
+       (let-values ([(d i) (char-set-diff+intersection cs1 cs2)])
+         (values (apply char-set-difference d more)
+                 (apply char-set-intersection i more)))]))
 
   (define char-set-adjoin! char-set-adjoin)
   (define char-set-delete! char-set-delete)
@@ -432,13 +435,13 @@
    [char-set-union char-sets0/c]
    [char-set-union! char-sets/c]
    [char-set-intersection char-sets0/c]
-   [char-set-intersection! char-sets/c]
+   [char-set-intersection! char-sets0/c]
    [char-set-difference char-sets/c]
-   [char-set-difference! char-sets+/c]
+   [char-set-difference! char-sets/c]
    [char-set-xor char-sets0/c]
    [char-set-xor! char-sets/c]
-   [char-set-diff+intersection char-sets+/c]
-   [char-set-diff+intersection! char-sets+/c])
+   [char-set-diff+intersection char-sets/c]
+   [char-set-diff+intersection! char-sets/c])
   (provide
    char-set:lower-case
    char-set:upper-case
diff --git a/collects/tests/mzscheme/char-set.ss b/collects/tests/mzscheme/char-set.ss
index 1c45b69c99..d586397ef0 100644
--- a/collects/tests/mzscheme/char-set.ss
+++ b/collects/tests/mzscheme/char-set.ss
@@ -251,8 +251,10 @@
 						 (char-set #\v #\b)))
 	   (test #t char-set= cs1 (char-set-diff (char-set #\U #\t #\a #\h #\v #\w) 
 						 (char-set #\v #\b)
-						 (char-set #\w))))])
+						 (char-set #\w)))
+           (test #t char-set= cs1 (char-set-diff (char-set #\U #\t #\a #\h))))])
     (go char-set-difference)
+    (go char-set-difference!)
     (go char-set-difference!))
 
   (let ([go 
@@ -267,7 +269,12 @@
 
   (let ([go 
 	 (lambda (char-set-diff+i)
-	   (test #t andmap char-set= (list cs1 (char-set #\v))
+	   (test #t andmap char-set= (list cs1 (char-set-union))
+		 (call-with-values
+		     (lambda ()
+		       (char-set-diff+i (char-set #\U #\t #\a #\h)))
+		   list))
+           (test #t andmap char-set= (list cs1 (char-set #\v))
 		 (call-with-values
 		     (lambda ()
 		       (char-set-diff+i (char-set #\U #\t #\a #\h #\v) 
@@ -281,6 +288,7 @@
 					(char-set #\w)))
 		   list)))])
     (go char-set-diff+intersection)
+    (go char-set-diff+intersection)
     (go char-set-diff+intersection!))
 
   )