diff --git a/quad2/struct.rkt b/quad2/struct.rkt
index 4de50867..14c7bf5a 100644
--- a/quad2/struct.rkt
+++ b/quad2/struct.rkt
@@ -32,4 +32,5 @@
   path
   numeric
   boolean
+  set
   unknown)
\ No newline at end of file