diff --git a/blackjax/mcmc/metrics.py b/blackjax/mcmc/metrics.py
index d86aec7d6..1e01e4559 100644
--- a/blackjax/mcmc/metrics.py
+++ b/blackjax/mcmc/metrics.py
@@ -65,8 +65,9 @@ def __call__(
         self,
         position: ArrayLikeTree,
         element: ArrayLikeTree,
-        inv: ArrayLikeTree,
-        trans: ArrayLikeTree,
+        *,
+        inv: bool,
+        trans: bool,
     ) -> ArrayLikeTree:
         ...