diff --git a/build-constraints.yaml b/build-constraints.yaml
index b0179dc3..6349c091 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -595,7 +595,7 @@ packages:
         - pointed
         - profunctors
         - promises
-        # - rcu # https://github.com/ekmett/rcu/issues/3
+        - rcu
         - recursion-schemes
         - reducers
         - reflection