diff --git a/format.c b/format.c
index 6dfec4b7..b9f89bb5 100644
--- a/format.c
+++ b/format.c
@@ -2197,6 +2197,11 @@ format_defaults_winlink(struct format_tree *ft, struct winlink *wl)
 	format_add(ft, "window_end_flag", "%d",
 	    !!(wl == RB_MAX(winlinks, &s->windows)));
 
+	if (server_check_marked() && marked_pane.wl == wl)
+	    format_add(ft, "window_marked_flag", "1");
+	else
+	    format_add(ft, "window_marked_flag", "0");
+
 	format_add(ft, "window_bell_flag", "%d",
 	    !!(wl->flags & WINLINK_BELL));
 	format_add(ft, "window_activity_flag", "%d",
diff --git a/tmux.1 b/tmux.1
index c4c5698e..8507ae75 100644
--- a/tmux.1
+++ b/tmux.1
@@ -4305,6 +4305,7 @@ The following variables are available, where appropriate:
 .It Li "window_last_flag" Ta "" Ta "1 if window is the last used"
 .It Li "window_layout" Ta "" Ta "Window layout description, ignoring zoomed window panes"
 .It Li "window_linked" Ta "" Ta "1 if window is linked across sessions"
+.It Li "window_marked_flag" Ta "" Ta "1 if window contains the marked pane"
 .It Li "window_name" Ta "#W" Ta "Name of window"
 .It Li "window_offset_x" Ta "" Ta "X offset into window if larger than client"
 .It Li "window_offset_y" Ta "" Ta "Y offset into window if larger than client"