diff --git a/src/noisepy/seis/scheduler.py b/src/noisepy/seis/scheduler.py
index af636dc1..e6846905 100644
--- a/src/noisepy/seis/scheduler.py
+++ b/src/noisepy/seis/scheduler.py
@@ -78,7 +78,7 @@ def initialize(self, initializer: Callable[[], List], shared_vars: int) -> List:
             logger.debug(f"RANK {rank}, vars = {vars}")
             return vars
 
-    def get_indices(self, items: list) -> list[int]:
+    def get_indices(self, items: list) -> List[int]:
         rank = self.comm.Get_rank()
         size = self.comm.Get_size()
         rank = self.comm.Get_rank()