diff --git a/collects/compiler/zo-marshal.ss b/collects/compiler/zo-marshal.ss
index 8091e93e1b..4102326db6 100644
--- a/collects/compiler/zo-marshal.ss
+++ b/collects/compiler/zo-marshal.ss
@@ -578,7 +578,7 @@
                           (if (memq 'preserves-marks flags) CLOS_PRESERVES_MARKS 0)
                           (if (memq 'is-method flags) CLOS_IS_METHOD 0)
                           (if (memq 'single-result flags) CLOS_SINGLE_RESULT 0))
-                       ((if rest? add1 0) num-params)
+                       ((if rest? add1 values) num-params)
                        max-let-depth
                        name
                        l)
diff --git a/collects/tests/mzscheme/zo-marshal.ss b/collects/tests/mzscheme/zo-marshal.ss
new file mode 100644
index 0000000000..610871f858
--- /dev/null
+++ b/collects/tests/mzscheme/zo-marshal.ss
@@ -0,0 +1,161 @@
+
+(load-relative "loadtest.ss")
+
+(Section 'zo-marshal)
+
+(require compiler/zo-parse
+         compiler/zo-marshal)
+
+(define (check expr val #:wrap [wrap values])
+  (let ([s (zo-marshal expr)])
+    (test expr zo-parse (open-input-bytes s))
+    (test val wrap (eval (parameterize ([read-accept-compiled #t])
+                           (read (open-input-bytes s)))))))
+
+(define (get-id id)
+  (primval-id
+   (compilation-top-code
+    (zo-parse (let ([s (open-output-bytes)])
+                (write (compile id) s)
+                (open-input-bytes (get-output-bytes s)))))))
+
+(define values-id (get-id #'values))
+(define object-name-id (get-id #'object-name))
+
+;; ----------------------------------------
+
+(define (make-simple e)
+  (make-compilation-top
+   10
+   (make-prefix 0 null null)
+   e))
+
+;; ----------------------------------------
+
+(check (make-simple 5)
+       5)
+
+(let ([ck (lambda (cl? o-cls?)
+            (check (make-simple (make-let-one 
+                                 51
+                                 (make-localref #f 0 cl? o-cls?)))
+                   51))])
+  (ck #f #f)
+  (ck #t #f)
+  (ck #f #t))
+
+
+(check (make-simple (make-let-one 
+                     15
+                     (make-boxenv
+                      0
+                      (make-localref #t 0 #f #f))))
+       15)
+
+(check (make-simple (make-let-void
+                     3
+                     #f
+                     (make-install-value
+                      1
+                      0
+                      #f
+                      503
+                      (make-boxenv
+                       0
+                       (make-localref #t 0 #f #f)))))
+       503)
+
+(check (make-simple (make-let-void
+                     3
+                     #f
+                     (make-install-value
+                      2
+                      1
+                      #f
+                      (make-application
+                       (make-primval values-id)
+                       (list 503
+                             507))
+                      (make-localref #f 2 #f #f))))
+       507)
+
+(check (make-simple (make-branch
+                     #t
+                     50
+                     -50))
+       50)
+
+(check (make-simple (make-branch
+                     #f
+                     50
+                     -50))
+       -50)
+
+;; ----------------------------------------
+
+(define (make-ab body)
+  (make-simple (make-let-void
+                2
+                #f
+                (make-let-rec
+                 (list
+                  (make-lam 'a
+                            null
+                            1
+                            '(val)
+                            #f
+                            #(1)
+                            10
+                            (make-branch
+                             (make-localref #f 1 #f #f)
+                             (make-localref #f 0 #f #f)
+                             59))
+                  (make-lam 'b
+                            null
+                            1
+                            '(val)
+                            #f
+                            #(0)
+                            10
+                            (make-localref #f 0 #f #f)))
+                 body))))
+
+(check (make-ab 517)
+       517)
+
+(check (make-ab (make-application
+                 (make-primval object-name-id)
+                 (list (make-localref #f 1 #f #f))))
+       'a)
+(check (make-ab (make-application
+                 (make-primval object-name-id)
+                 (list (make-localref #f 2 #f #f))))
+       'b)
+
+(check (make-ab (make-application
+                 (make-localref #f 1 #f #f)
+                 (list #f)))
+       59)
+(check (make-ab (make-application
+                 (make-primval object-name-id)
+                 (list
+                  (make-application
+                   (make-localref #f 2 #f #f)
+                   (list #t)))))
+       'b)
+(check (make-ab (make-application
+                 (make-primval object-name-id)
+                 (list
+                  (make-application
+                   (make-application
+                    (make-localref #f 3 #f #f)
+                    (list #t))
+                   (list -5)))))
+       'a)
+
+;; ----------------------------------------
+
+
+;; ----------------------------------------
+
+(report-errs)