diff --git a/build-constraints.yaml b/build-constraints.yaml
index 0ab5775f..6db0dd3f 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -1012,7 +1012,7 @@ expected-test-failures:
 
     # Seems to depend on mtl being installed in user package database, which
     # isn't always the case (e.g., build server)
-    - mtl
+    - happy
 
     # https://github.com/jberryman/directory-tree/issues/4
     - directory-tree