diff --git a/collects/mzlib/struct.ss b/collects/mzlib/struct.ss
index f055d2a..85bf0aa 100644
--- a/collects/mzlib/struct.ss
+++ b/collects/mzlib/struct.ss
@@ -7,54 +7,64 @@
   (require-for-syntax (lib "struct.ss" "syntax")
 		      (lib "stx.ss" "syntax"))
 
+  ;; copy-struct expands to `do-copy-struct' to delay the expansion
+  ;;  in an internal-definition context. (The `begin0' wrapper
+  ;;  effectively declares the form to be an expression.)
   (define-syntax (copy-struct stx)
     (syntax-case stx ()
-      [(_ info structure (accessor-name new-val) ...)
-       (let ([ans (syntax->list  #'((accessor-name new-val) ...))])
-	 (unless (identifier? #'info)
-	   (raise-syntax-error #f "not an identifier for structure type" stx #'info))
-	 (for-each (lambda (an)
-		     (unless (identifier? (stx-car an))
-		       (raise-syntax-error #f "not an identifier for accessor name" stx (stx-car an))))
-		   ans)
-	 
-	 ;; new-binding-for : syntax[field-name] -> (union syntax[expression] #f)
-	 (let ((new-binding-for 
-		(lambda (f)
-		  (ormap (lambda (x) 
-			   (if (eq? (syntax-object->datum (stx-car x)) (syntax-object->datum f)) 
-			       (cadr (syntax-e x)) 
-			       #f))
-			 ans))))
-	   
-	   (let-values ([(construct pred accessors)
-			 (let ([v (syntax-local-value #'info (lambda () #f))])
-			   (unless (struct-declaration-info? v)
-			     (raise-syntax-error #f "identifier is not bound to a structure type" stx #'info))
-			   (values (cadr v)
-				   (caddr v)
-				   (cadddr v)))]
-			[(as) (map (lambda (an) (stx-car an)) ans)])
-	     (for-each 
-	      (lambda (field)
-		(unless (ormap (lambda (f2) (module-or-top-identifier=? field f2)) accessors)
-		  (raise-syntax-error #f "accessor name not associated with the given structure type" stx field)))
-	      as)
-	     
-	     (let ((dupe (check-duplicate-identifier as)))
-	       (when dupe 
-		 (raise-syntax-error #f 
-				     "duplicate field assignment" 
-				     stx 
-				     dupe)))
-	     
-	     ;; the actual result
-	     #`(let ((the-struct structure))
-		 (if (#,pred the-struct)
-		     (#,construct
-		      #,@(map 
-			  (lambda (field) (or (new-binding-for field) #`(#,field the-struct)))
-			  (reverse accessors)))
-		     (raise-type-error '_  #,(format "struct:~a" (syntax-object->datum #'info)) the-struct))))))])))
+      [_ #'(begin0 (do-copy-struct _))]))
+  
+  (define-syntax (do-copy-struct dstx)
+    (syntax-case dstx ()
+      [(_ stx)
+       (let ([stx #'stx])
+	 (syntax-case stx ()
+	   [(_ info structure (accessor-name new-val) ...)
+	    (let ([ans (syntax->list  #'((accessor-name new-val) ...))])
+	      (unless (identifier? #'info)
+		(raise-syntax-error #f "not an identifier for structure type" stx #'info))
+	      (for-each (lambda (an)
+			  (unless (identifier? (stx-car an))
+			    (raise-syntax-error #f "not an identifier for accessor name" stx (stx-car an))))
+			ans)
+	      
+	      ;; new-binding-for : syntax[field-name] -> (union syntax[expression] #f)
+	      (let ((new-binding-for 
+		     (lambda (f)
+		       (ormap (lambda (x) 
+				(if (eq? (syntax-object->datum (stx-car x)) (syntax-object->datum f)) 
+				    (cadr (syntax-e x)) 
+				    #f))
+			      ans))))
+		
+		(let-values ([(construct pred accessors)
+			      (let ([v (syntax-local-value #'info (lambda () #f))])
+				(unless (struct-declaration-info? v)
+				  (raise-syntax-error #f "identifier is not bound to a structure type" stx #'info))
+				(values (cadr v)
+					(caddr v)
+					(cadddr v)))]
+			     [(as) (map (lambda (an) (stx-car an)) ans)])
+		  (for-each 
+		   (lambda (field)
+		     (unless (ormap (lambda (f2) (module-or-top-identifier=? field f2)) accessors)
+		       (raise-syntax-error #f "accessor name not associated with the given structure type" stx field)))
+		   as)
+		  
+		  (let ((dupe (check-duplicate-identifier as)))
+		    (when dupe 
+		      (raise-syntax-error #f 
+					  "duplicate field assignment" 
+					  stx 
+					  dupe)))
+		  
+		  ;; the actual result
+		  #`(let ((the-struct structure))
+		      (if (#,pred the-struct)
+			  (#,construct
+			   #,@(map 
+			       (lambda (field) (or (new-binding-for field) #`(#,field the-struct)))
+			       (reverse accessors)))
+			  (raise-type-error '_  #,(format "struct:~a" (syntax-object->datum #'info)) the-struct))))))]))])))
 
     
\ No newline at end of file
diff --git a/collects/tests/mzscheme/structlib.ss b/collects/tests/mzscheme/structlib.ss
new file mode 100644
index 0000000..d41c6ae
--- /dev/null
+++ b/collects/tests/mzscheme/structlib.ss
@@ -0,0 +1,35 @@
+
+(load-relative "loadtest.ss")
+
+(SECTION 'structlib)
+
+(require (lib "struct.ss"))
+
+(let ([now (seconds->date (current-seconds))])
+  (test #t equal? now (copy-struct date now))
+  (test #f equal? now (copy-struct date now (date-second -1)))
+  (test -1 date-second (copy-struct date now (date-second -1)))
+  (test (date-year now) date-year (copy-struct date now (date-second -1))))
+
+(err/rt-test (copy-struct date 10))
+(err/rt-test (copy-struct date 10 (date-second 0)))
+
+(syntax-test #'copy-struct)
+(syntax-test #'(copy-struct))
+(syntax-test #'(copy-struct date))
+(syntax-test #'(copy-struct date 10 foo))
+(syntax-test #'(copy-struct date 10 . foo))
+(syntax-test #'(copy-struct date 10 (foo)))
+(syntax-test #'(copy-struct date 10 (foo . bar)))
+
+(syntax-test #'(copy-struct x 10))
+(syntax-test #'(copy-struct date 10 (date-foo 12)))
+(syntax-test #'(copy-struct date 10 (date-second 12) (date-yeeer 10)))
+
+(let ([v (let ()
+	   (define-struct a (b c) (make-inspector))
+	   ;; This `copy-struct' is expanded in an internal-defn context
+	   (copy-struct a (make-a 1 2) (a-c 13)))])
+  (test #(struct:a 1 13) struct->vector v))
+
+(report-errs)