diff --git a/build-constraints.yaml b/build-constraints.yaml
index 688852ff..195eb749 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -8151,6 +8151,8 @@ expected-test-failures:
 
     # Please review the sections above before adding packages to a new section or to Misc.
 
+    - fourmolu # https://github.com/commercialhaskell/stackage/issues/6596
+
 # end of expected-test-failures