diff --git a/ordered_set/__init__.py b/ordered_set/__init__.py
index ccd1cbf..f443858 100644
--- a/ordered_set/__init__.py
+++ b/ordered_set/__init__.py
@@ -219,11 +219,11 @@ def update(self, sequence: SetLike[T]) -> int:
         return item_index
 
     @overload
-    def index(self, key: Sequence[T]) -> List[int]:
+    def index(self, key: T) -> int:
         ...
 
     @overload
-    def index(self, key: T) -> int:
+    def index(self, key: Sequence[T]) -> List[int]:
         ...
 
     # concrete implementation