diff --git a/lib/Quox/Syntax/Subst.idr b/lib/Quox/Syntax/Subst.idr
index a14c232..976f7bb 100644
--- a/lib/Quox/Syntax/Subst.idr
+++ b/lib/Quox/Syntax/Subst.idr
@@ -133,7 +133,7 @@ cmpShape : Subst env from1 to -> Subst env from2 to ->
 cmpShape (Shift by) (Shift bz) = cmpLen by bz
 cmpShape (Shift _)  (_ ::: _)  = Left LT
 cmpShape (_ ::: _)  (Shift _)  = Left GT
-cmpShape (_ ::: th) (_ ::: ph) = cong S <$> cmpShape th ph
+cmpShape (_ ::: th) (_ ::: ph) = map (\x => cong S x) $ cmpShape th ph
 
 
 public export
diff --git a/pack.toml b/pack.toml
index 35f81cf..ae96ef9 100644
--- a/pack.toml
+++ b/pack.toml
@@ -1,4 +1,4 @@
-collection = "nightly-230622"
+collection = "nightly-230711"
 
 [custom.all.tap]
 type = "git"