diff --git a/src/textual/widgets/_list_view.py b/src/textual/widgets/_list_view.py
index 1fdccf6814..b102a17d20 100644
--- a/src/textual/widgets/_list_view.py
+++ b/src/textual/widgets/_list_view.py
@@ -39,6 +39,7 @@ class ListView(VerticalScroll, can_focus=True, can_focus_children=False):
     """
 
     index = reactive[Optional[int]](0, always_update=True)
+    """The index of the currently highlighted item."""
 
     class Highlighted(Message):
         """Posted when the highlighted item changes.