diff --git a/collects/mzlib/private/unitidmap.ss b/collects/mzlib/private/unitidmap.ss
index a0eb58bdcc..718ba07eb6 100644
--- a/collects/mzlib/private/unitidmap.ss
+++ b/collects/mzlib/private/unitidmap.ss
@@ -28,7 +28,7 @@
 	   (binding
 	    the-binder (car (syntax-e sstx))
 	    (datum->syntax-object
-	     set!-stx
+	     sstx
 	     (cons unbox-stx (cdr (syntax-e sstx)))
 	     sstx))])))))