diff --git a/sievelib/tools.py b/sievelib/tools.py
index 250289d..a139c39 100644
--- a/sievelib/tools.py
+++ b/sievelib/tools.py
@@ -1,7 +1,9 @@
 """Some tools."""
 
+from typing import List
 
-def to_list(stringlist: str, unquote: bool = True) -> list[str]:
+
+def to_list(stringlist: str, unquote: bool = True) -> List[str]:
     """Convert a string representing a list to real list."""
     stringlist = stringlist[1:-1]
     return [