diff --git a/lisp/minibuffer.el b/lisp/minibuffer.el
index 00d4560865..f38db6d278 100644
--- a/lisp/minibuffer.el
+++ b/lisp/minibuffer.el
@@ -1407,18 +1407,26 @@ completion--in-region-1
    ;; and this command is repeated, scroll that window.
    ((and (window-live-p minibuffer-scroll-window)
          (eq t (frame-visible-p (window-frame minibuffer-scroll-window))))
-    (let ((window minibuffer-scroll-window)
-          (reverse (equal (this-command-keys) [backtab])))
+    (let ((window minibuffer-scroll-window))
       (with-current-buffer (window-buffer window)
-        (if (pos-visible-in-window-p (if reverse (point-min) (point-max)) window)
-            ;; If end or beginning is in view, scroll up to the
-            ;; beginning or end respectively.
-            (if reverse
-                (set-window-point window (point-max))
-              (set-window-start window (point-min) nil))
-          ;; Else scroll down one screen.
-          (with-selected-window window
-            (if reverse (scroll-down) (scroll-up))))
+        (cond
+         ;; here this is possible only when second-tab, so jump now.
+         (completion-auto-select
+          (switch-to-completions))
+         ;; reverse tab
+         ((equal (this-command-keys) [backtab])
+          (if (pos-visible-in-window-p (point-min) window)
+              ;; If beginning is in view, scroll up to the end
+              (set-window-point window (point-max))
+            ;; Else scroll down one screen.
+            (with-selected-window window (scroll-down))))
+         ;; normal tab
+         (t
+          (if (pos-visible-in-window-p (point-max) window)
+              ;; If end is in view, scroll up to the end
+              (set-window-start window (point-min) nil)
+            ;; Else scroll down one screen.
+            (with-selected-window window (scroll-up)))))
         nil)))
    ;; If we're cycling, keep on cycling.
    ((and completion-cycling completion-all-sorted-completions)
diff --git a/lisp/simple.el b/lisp/simple.el
index 9a8ed0bb75..f229608690 100644
--- a/lisp/simple.el
+++ b/lisp/simple.el
@@ -9144,6 +9144,14 @@ completion-wrap-movement
   :version "29.1"
   :group 'completion)
 
+(defcustom completion-auto-select nil
+  "Non-nil means to automatically select the *Completions* buffer."
+  :type '(choice (const :tag "Select window" t)
+                 (const :tag "Disabled" nil)
+                 (const :tag "Select window on second-tab" second-tab))
+  :version "29.1"
+  :group 'completion)
+
 (defun previous-completion (n)
   "Move to the previous item in the completion list.
 With prefix argument N, move back N items (negative N means move
@@ -9365,12 +9373,6 @@ completion-show-help
   :version "22.1"
   :group 'completion)
 
-(defcustom completion-auto-select nil
-  "Non-nil means to automatically select the *Completions* buffer."
-  :type 'boolean
-  :version "29.1"
-  :group 'completion)
-
 ;; This function goes in completion-setup-hook, so that it is called
 ;; after the text of the completion list buffer is written.
 (defun completion-setup-function ()
@@ -9411,8 +9413,8 @@ completion-setup-function
 	(insert (substitute-command-keys
 		 "In this buffer, type \\[choose-completion] to \
 select the completion near point.\n\n")))))
-  (when completion-auto-select
-    (switch-to-completions)))
+  (if (eq completion-auto-select t)
+      (switch-to-completions)))
 
 (add-hook 'completion-setup-hook #'completion-setup-function)