diff --git a/unpack-assoc.scm b/unpack-assoc.scm
index 3ba7cc3..16256c6 100644
--- a/unpack-assoc.scm
+++ b/unpack-assoc.scm
@@ -53,7 +53,7 @@
 (define-syntax unpack-using/set
   (syntax-rules ()
     ((_ (sets ...))
-     (begin sets ...))
+     (begin sets ... #f))
     ((_ (sets ...) rule rules ...)
      (unpack-using/set (sets ... (unpack-using/rule rule)) rules ...))))