diff --git a/middle_end/flambda2/from_lambda/lambda_to_lambda_transforms.mli b/middle_end/flambda2/from_lambda/lambda_to_lambda_transforms.mli
index cd3346a5e8e..4ea169908bb 100644
--- a/middle_end/flambda2/from_lambda/lambda_to_lambda_transforms.mli
+++ b/middle_end/flambda2/from_lambda/lambda_to_lambda_transforms.mli
@@ -44,6 +44,7 @@ val switch_for_if_then_else :
 val transform_primitive :
   Lambda_to_flambda_env.t ->
   Lambda.primitive ->
+  (* CR mshinwell: consider [Ident.t list] instead for the arguments. *)
   Lambda.lambda list ->
   Lambda.scoped_location ->
   Lambda_to_flambda_env.t * primitive_transform_result