diff --git a/seqio/dataset_providers.py b/seqio/dataset_providers.py
index eda91545..2415e101 100644
--- a/seqio/dataset_providers.py
+++ b/seqio/dataset_providers.py
@@ -1855,7 +1855,7 @@ def source_info(self) -> Optional[SourceInfo]:
     return self._source_info
 
   @property
-  def tasks(self) -> Sequence[Task]:
+  def tasks(self) -> list[Task]:
     sub_tasks = (mix.tasks for mix in self._sub_mixtures)
     return list(sorted(set(sum(sub_tasks, self._tasks)), key=lambda t: t.name))