diff --git a/cmd-join-pane.c b/cmd-join-pane.c
index 9802083d..904d2c29 100644
--- a/cmd-join-pane.c
+++ b/cmd-join-pane.c
@@ -160,7 +160,7 @@ cmd_join_pane_exec(struct cmd *self, struct cmdq_item *item)
 		server_status_session(dst_s);
 
 	if (window_count_panes(src_w) == 0)
-		server_kill_window(src_w);
+		server_kill_window(src_w, 1);
 	else
 		notify_window("window-layout-changed", src_w);
 	notify_window("window-layout-changed", dst_w);
diff --git a/cmd-kill-window.c b/cmd-kill-window.c
index 68139faa..430f667e 100644
--- a/cmd-kill-window.c
+++ b/cmd-kill-window.c
@@ -57,9 +57,10 @@ cmd_kill_window_exec(struct cmd *self, struct cmdq_item *item)
 {
 	struct args		*args = cmd_get_args(self);
 	struct cmd_find_state	*target = cmdq_get_target(item);
-	struct winlink		*wl = target->wl, *wl2, *wl3;
+	struct winlink		*wl = target->wl, *loop;
 	struct window		*w = wl->window;
 	struct session		*s = target->s;
+	u_int			 found;
 
 	if (cmd_get_entry(self) == &cmd_unlink_window_entry) {
 		if (!args_has(args, 'k') && !session_is_linked(s, w)) {
@@ -67,16 +68,43 @@ cmd_kill_window_exec(struct cmd *self, struct cmdq_item *item)
 			return (CMD_RETURN_ERROR);
 		}
 		server_unlink_window(s, wl);
-	} else {
-		if (args_has(args, 'a')) {
-			RB_FOREACH_SAFE(wl2, winlinks, &s->windows, wl3) {
-				if (wl != wl2)
-					server_kill_window(wl2->window);
-			}
-		} else
-			server_kill_window(wl->window);
+		recalculate_sizes();
+		return (CMD_RETURN_NORMAL);
 	}
 
-	recalculate_sizes();
+	if (args_has(args, 'a')) {
+		if (RB_PREV(winlinks, &s->windows, wl) == NULL &&
+		    RB_NEXT(winlinks, &s->windows, wl) == NULL)
+			return (CMD_RETURN_NORMAL);
+
+		/* Kill all windows except the current one. */
+		do {
+			found = 0;
+			RB_FOREACH(loop, winlinks, &s->windows) {
+				if (loop->window != wl->window) {
+					server_kill_window(loop->window, 0);
+					found++;
+					break;
+				}
+			}
+		} while (found != 0);
+
+		/*
+		 * If the current window appears in the session more than once,
+		 * kill it as well.
+		 */
+		found = 0;
+		RB_FOREACH(loop, winlinks, &s->windows) {
+			if (loop->window == wl->window)
+				found++;
+		}
+		if (found > 1)
+			server_kill_window(wl->window, 0);
+
+		server_renumber_all();
+		return (CMD_RETURN_NORMAL);
+	}
+
+	server_kill_window(wl->window, 1);
 	return (CMD_RETURN_NORMAL);
 }
diff --git a/server-fn.c b/server-fn.c
index d66aed0b..84ec4123 100644
--- a/server-fn.c
+++ b/server-fn.c
@@ -183,7 +183,7 @@ server_kill_pane(struct window_pane *wp)
 	struct window	*w = wp->window;
 
 	if (window_count_panes(w) == 1) {
-		server_kill_window(w);
+		server_kill_window(w, 1);
 		recalculate_sizes();
 	} else {
 		server_unzoom_window(w);
@@ -195,19 +195,15 @@ server_kill_pane(struct window_pane *wp)
 }
 
 void
-server_kill_window(struct window *w)
+server_kill_window(struct window *w, int renumber)
 {
-	struct session		*s, *next_s, *target_s;
-	struct session_group	*sg;
-	struct winlink		*wl;
-
-	next_s = RB_MIN(sessions, &sessions);
-	while (next_s != NULL) {
-		s = next_s;
-		next_s = RB_NEXT(sessions, &sessions, s);
+	struct session	*s, *s1;
+	struct winlink	*wl;
 
+	RB_FOREACH_SAFE(s, sessions, &sessions, s1) {
 		if (!session_has(s, w))
 			continue;
+
 		server_unzoom_window(w);
 		while ((wl = winlink_find_by_window(&s->windows, w)) != NULL) {
 			if (session_detach(s, wl)) {
@@ -217,17 +213,35 @@ server_kill_window(struct window *w)
 				server_redraw_session_group(s);
 		}
 
-		if (options_get_number(s->options, "renumber-windows")) {
-			if ((sg = session_group_contains(s)) != NULL) {
-				TAILQ_FOREACH(target_s, &sg->sessions, gentry)
-					session_renumber_windows(target_s);
-			} else
-				session_renumber_windows(s);
-		}
+		if (renumber)
+			server_renumber_session(s);
 	}
 	recalculate_sizes();
 }
 
+void
+server_renumber_session(struct session *s)
+{
+	struct session_group	*sg;
+
+	if (options_get_number(s->options, "renumber-windows")) {
+		if ((sg = session_group_contains(s)) != NULL) {
+			TAILQ_FOREACH(s, &sg->sessions, gentry)
+			    session_renumber_windows(s);
+		} else
+			session_renumber_windows(s);
+	}
+}
+
+void
+server_renumber_all(void)
+{
+	struct session	*s;
+
+	RB_FOREACH(s, sessions, &sessions)
+		server_renumber_session(s);
+}
+
 int
 server_link_window(struct session *src, struct winlink *srcwl,
     struct session *dst, int dstidx, int killflag, int selectflag,
@@ -354,7 +368,7 @@ server_destroy_pane(struct window_pane *wp, int notify)
 	window_remove_pane(w, wp);
 
 	if (TAILQ_EMPTY(&w->panes))
-		server_kill_window(w);
+		server_kill_window(w, 1);
 	else
 		server_redraw_window(w);
 }
diff --git a/tmux.h b/tmux.h
index 0a1a740b..a8c67051 100644
--- a/tmux.h
+++ b/tmux.h
@@ -2420,7 +2420,9 @@ void	 server_lock(void);
 void	 server_lock_session(struct session *);
 void	 server_lock_client(struct client *);
 void	 server_kill_pane(struct window_pane *);
-void	 server_kill_window(struct window *);
+void	 server_kill_window(struct window *, int);
+void	 server_renumber_session(struct session *);
+void	 server_renumber_all(void);
 int	 server_link_window(struct session *,
 	     struct winlink *, struct session *, int, int, int, char **);
 void	 server_unlink_window(struct session *, struct winlink *);
diff --git a/window-tree.c b/window-tree.c
index 32b94e15..384cf392 100644
--- a/window-tree.c
+++ b/window-tree.c
@@ -1054,7 +1054,7 @@ window_tree_kill_each(__unused void *modedata, void *itemdata,
 		break;
 	case WINDOW_TREE_WINDOW:
 		if (wl != NULL)
-			server_kill_window(wl->window);
+			server_kill_window(wl->window, 1);
 		break;
 	case WINDOW_TREE_PANE:
 		if (wp != NULL)