diff --git a/lisp/tab-bar.el b/lisp/tab-bar.el
index 6720d82b47..1741173bbe 100644
--- a/lisp/tab-bar.el
+++ b/lisp/tab-bar.el
@@ -139,16 +139,21 @@ Possible modifier keys are `control', `meta', `shift', `hyper', `super' and
   :global t
   ;; It's defined in C/cus-start, this stops the d-m-m macro defining it again.
   :variable tab-bar-mode
-  (let ((val (if tab-bar-mode 1 0)))
+
+  ;; Set frame parameters.
+  (let ((defaultval (if (and tab-bar-mode tab-bar-show) 1 0)))
     (dolist (frame (frame-list))
-      (set-frame-parameter frame 'tab-bar-lines val))
-    ;; If the user has given `default-frame-alist' a `tab-bar-lines'
-    ;; parameter, replace it.
-    (if (assq 'tab-bar-lines default-frame-alist)
-        (setq default-frame-alist
-              (cons (cons 'tab-bar-lines val)
-                    (assq-delete-all 'tab-bar-lines
-                                     default-frame-alist)))))
+      (let ((frameval (if (natnump tab-bar-show)
+                          (if (and defaultval
+                                   (> (length (funcall tab-bar-tabs-function frame)) tab-bar-show))
+                              1 0)
+                        defaultval)))
+        (set-frame-parameter frame 'tab-bar-lines frameval)))
+    (let ((newframeval (if (and defaultval (eq tab-bar-show t)) 1 0)))
+      (setq default-frame-alist
+            (cons (cons 'tab-bar-lines newframeval)
+                  (assq-delete-all 'tab-bar-lines default-frame-alist)))))
+
   (when tab-bar-mode
     (tab-bar--load-buttons))
   (if tab-bar-mode
@@ -251,16 +256,7 @@ you can use the command `toggle-frame-tab-bar'."
   :set (lambda (sym val)
          (set-default sym val)
          ;; Preload button images
-         (tab-bar-mode 1)
-         ;; Then handle each frame individually
-         (dolist (frame (frame-list))
-           (set-frame-parameter
-            frame 'tab-bar-lines
-            (if (or (eq val t)
-                    (and (natnump val)
-                         (> (length (funcall tab-bar-tabs-function frame))
-                            val)))
-                1 0))))
+         (tab-bar-mode 1))
   :group 'tab-bar
   :version "27.1")