diff --git a/build-constraints.yaml b/build-constraints.yaml
index c121ed83..3a1e2843 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -7768,7 +7768,7 @@ expected-test-failures:
     - greskell
     - greskell-core
     - headroom
-    - heterocephalus
+    - heterocephalus # https://github.com/commercialhaskell/stackage/issues/6464
     - hint
     - hledger-lib
     - iproute