diff --git a/tmux.1 b/tmux.1
index b2171b4c..847e3e1b 100644
--- a/tmux.1
+++ b/tmux.1
@@ -3352,7 +3352,6 @@ All the notifications listed in the
 section are hooks (without any arguments), except
 .Ic %exit .
 The following additional hooks are available:
-.Pp
 .Bl -tag -width "XXXXXXXXXXXXXXXXXXXXXX"
 .It alert-activity
 Run when a window has activity.
diff --git a/window-tree.c b/window-tree.c
index b7626c86..164f0aad 100644
--- a/window-tree.c
+++ b/window-tree.c
@@ -931,7 +931,7 @@ window_tree_command_callback(struct client *c, void *modedata, const char *s,
 {
 	struct window_tree_modedata	*data = modedata;
 
-	if (data->dead)
+	if (s == NULL || data->dead)
 		return (0);
 
 	data->entered = s;