diff --git a/build-constraints.yaml b/build-constraints.yaml
index 255a49ca..6ad0be64 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -1719,7 +1719,7 @@ packages:
     "Fumiaki Kinoshita <fumiexcel@gmail.com> @fumieval":
         - boundingboxes
         - control-bool
-        - extensible
+        # - extensible # BLOCKED freer-effects compilation failure
         - monad-skeleton
         - objective
         - witherable