diff --git a/src/main.c b/src/main.c
index 66726d2..6581ba9 100644
--- a/src/main.c
+++ b/src/main.c
@@ -1376,6 +1376,9 @@
 	    for (wp = (tp == curtab)
 		    ? firstwin : tp->tp_firstwin; wp != NULL; wp = wp->w_next)
 	    {
+		if (wp->w_buffer == NULL)
+		    /* Autocmd must have close the buffer already, skip. */
+		    continue;
 		buf = wp->w_buffer;
 		if (buf->b_changedtick != -1)
 		{
diff --git a/src/version.c b/src/version.c
index c9bf6de..375b07d 100644
--- a/src/version.c
+++ b/src/version.c
@@ -726,6 +726,8 @@
 static int included_patches[] =
 {   /* Add new patch number below this line */
 /**/
+    765,
+/**/
     764,
 /**/
     763,
diff --git a/src/window.c b/src/window.c
index e37450d..b5d4afd 100644
--- a/src/window.c
+++ b/src/window.c
@@ -2276,9 +2276,15 @@
 #endif
     }
 
+    if (only_one_window() && win_valid(win) && win->w_buffer == NULL
+	    && (last_window() || curtab != prev_curtab
+		|| close_last_window_tabpage(win, free_buf, prev_curtab)))
+	/* Autocommands have close all windows, quit now. */
+	getout(0);
+
     /* Autocommands may have closed the window already, or closed the only
      * other window or moved to another tab page. */
-    if (!win_valid(win) || last_window() || curtab != prev_curtab
+    else if (!win_valid(win) || last_window() || curtab != prev_curtab
 	    || close_last_window_tabpage(win, free_buf, prev_curtab))
 	return;
 
@@ -6282,7 +6288,8 @@
 	return FALSE;
 
     for (wp = firstwin; wp != NULL; wp = wp->w_next)
-	if ((!((wp->w_buffer->b_help && !curbuf->b_help)
+	if (wp->w_buffer != NULL
+		&& (!((wp->w_buffer->b_help && !curbuf->b_help)
 # ifdef FEAT_QUICKFIX
 		    || wp->w_p_pvw
 # endif