diff --git a/lisp/custom.el b/lisp/custom.el
index 9bd9712b65c..2e42ea73c14 100644
--- a/lisp/custom.el
+++ b/lisp/custom.el
@@ -1137,6 +1137,7 @@ Every theme X has a property `provide-theme' whose value is \"X-theme\".
 The command `customize-create-theme' writes theme files into this
 directory.  By default, Emacs searches for custom themes in this
 directory first---see `custom-theme-load-path'."
+  :initialize #'custom-initialize-delay
   :type 'string
   :group 'customize
   :version "22.1")