diff --git a/collects/mzlib/unit.ss b/collects/mzlib/unit.ss
index 8a2d829..48ba229 100644
--- a/collects/mzlib/unit.ss
+++ b/collects/mzlib/unit.ss
@@ -123,7 +123,8 @@
   (define-for-syntax (build-val+macro-defs sig)
     (with-syntax ([(((int-ivar . ext-ivar) ...)
                     ((((int-vid . ext-vid) ...) . vbody) ...)
-                    ((((int-sid . ext-sid) ...) . sbody) ...))
+                    ((((int-sid . ext-sid) ...) . sbody) ...)
+                    (((int-cid . ext-cid) . cbody) ...))
                    (map-sig (lambda (x) x)
                             (make-syntax-introducer)
                             sig)])