diff --git a/lisp/cus-edit.el b/lisp/cus-edit.el
index 7932031..299bae4 100644
--- a/lisp/cus-edit.el
+++ b/lisp/cus-edit.el
@@ -4710,6 +4710,13 @@ custom-group-state-update
 
 ;;; Reading and writing the custom file.
 
+;;;###autoload
+(defcustom custom-file-load-p t
+  "Load `custom-file' if it is not nil.
+Set this variable to `nil' if you want to define `custom-file' but not load it.
+This was possible. As per the old definition,someone could just define the variable
+and not load the file.")
+
 ;;;###autoload
 (defcustom custom-file nil
   "File used for storing customization information.
@@ -4722,10 +4729,12 @@ custom-file
 something like the following in your init file:
 
 (setq custom-file \"~/.config/emacs-custom.el\")
-(load custom-file)
 
-Note that both lines are necessary: the first line tells Custom to
-save all customizations in this file, but does not load it.
+This will load `custom-file' after the `user-init-file' if
+a) the file exists,
+b) `custom-file-load-p' is `t', and
+c) it was not loaded before explicitly with
+  (load-file custom-file).
 
 When you change this variable outside Custom, look in the
 previous custom file (usually your init file) for the
diff --git a/lisp/startup.el b/lisp/startup.el
index 9f0b23c..472e5f7 100644
--- a/lisp/startup.el
+++ b/lisp/startup.el
@@ -1494,6 +1494,17 @@ command-line
     (when (featurep 'native-compile)
       (startup--update-eln-cache))
 
+    ;; Load the `custom-file' if it was not loaded before (see documentation)
+
+    ;; if the user defined the custom-file and didn't reset `custom-file-load-p'
+    (when (and custom-file custom-file-load-p)
+      ;; make sure that you get the expanded custom-file name
+      ;; because that's what appears in `load-history'
+      (let ((real-custom-file (expand-file-name custom-file)))
+        ;; if it was loaded, assoc will return non-nil
+        (unless (assoc real-custom-file load-history)
+          (load real-custom-file))))
+
     (when (and deactivate-mark transient-mark-mode)
       (with-current-buffer (window-buffer)
         (deactivate-mark)))