diff --git a/tvix/eval/src/builtins/mod.rs b/tvix/eval/src/builtins/mod.rs
index 89ab5edb1..fa84afb70 100644
--- a/tvix/eval/src/builtins/mod.rs
+++ b/tvix/eval/src/builtins/mod.rs
@@ -588,6 +588,7 @@ mod pure_builtins {
         _algo: Value,
         _string: Value,
     ) -> Result<Value, ErrorKind> {
+        // FIXME: propagate contexts here.
         Ok(Value::Catchable(CatchableErrorKind::UnimplementedFeature(
             "hashString".to_string(),
         )))