diff --git a/mmdet/datasets/ade20k.py b/mmdet/datasets/ade20k.py
index 4831baaf5cd..dd49481a55e 100644
--- a/mmdet/datasets/ade20k.py
+++ b/mmdet/datasets/ade20k.py
@@ -1,5 +1,6 @@
 # Copyright (c) OpenMMLab. All rights reserved.
 import os.path as osp
+from typing import List
 
 from mmengine import fileio
 
@@ -220,11 +221,11 @@ def __init__(self,
         super().__init__(
             img_suffix=img_suffix, seg_map_suffix=seg_map_suffix, **kwargs)
 
-    def load_data_list(self) -> list[dict]:
+    def load_data_list(self) -> List[dict]:
         """Load annotation from directory or annotation file.
 
         Returns:
-            list[dict]: All data info of dataset.
+            List[dict]: All data info of dataset.
         """
         data_list = []
         img_dir = self.data_prefix.get('img_path', None)