diff --git a/conllu/models.py b/conllu/models.py
index <HASH>..<HASH> 100644
--- a/conllu/models.py
+++ b/conllu/models.py
@@ -117,7 +117,7 @@ class TokenList(T.List[Token]):
         token = self._dict_to_token_and_set_defaults(token)
         super(TokenList, self).append(token)
 
-    def insert(self, i: int, token: T.Union[dict, Token]) -> None:
+    def insert(self, i: 'SupportsIndex', token: T.Union[dict, Token]) -> None:
         token = self._dict_to_token_and_set_defaults(token)
         super(TokenList, self).insert(i, token)
Change type back to make newer mypy happy.