diff --git a/kitty/cmds.py b/kitty/cmds.py
index 93020b6d0..dedec58cb 100644
--- a/kitty/cmds.py
+++ b/kitty/cmds.py
@@ -44,7 +44,8 @@ You can use the |_ ls| command to get a list of windows. Note that for
 numeric fields such as id, pid and num the expression is interpreted as a number,
 not a regular expression. The field num refers to the window position in the current tab,
 starting from zero and counting clockwise (this is the same as the order in which the
-windows are reported by the |_ ls| command).
+windows are reported by the |_ ls| command). The window id of the current window
+is available as the KITTY_WINDOW_ID environment variable.
 '''
 MATCH_TAB_OPTION = '''\
 --match -m