diff --git a/crates/aiken-lang/src/tipo/environment.rs b/crates/aiken-lang/src/tipo/environment.rs
index 8b991f86..9fb16b41 100644
--- a/crates/aiken-lang/src/tipo/environment.rs
+++ b/crates/aiken-lang/src/tipo/environment.rs
@@ -1216,6 +1216,7 @@ impl<'a> Environment<'a> {
             return Ok(());
         }
 
+        // TODO: maybe we also care to check is_link?
         if allow_cast
             && (t1.is_data() || t2.is_data())
             && !(t1.is_unbound() || t2.is_unbound())