diff --git a/build-constraints.yaml b/build-constraints.yaml
index fe4b62a6..ac718ef9 100644
--- a/build-constraints.yaml
+++ b/build-constraints.yaml
@@ -554,7 +554,7 @@ packages:
         - monad-products
         - monad-st
         - monad-st
-        - mtl
+        - mtl < 2.2
         - nats
         - numeric-extras
         - parsers