-this mode. (Not all major modes have one.) Only the (still
-experimental and unadvertised) command @code{customize-mode} currently
-uses this. @code{define-derived-mode} does @emph{not} automatically
-define the specified customization group.
+this mode. (Not all major modes have one.) The command
+@code{customize-mode} uses this. @code{define-derived-mode} does
+@emph{not} automatically define the specified customization group.
+
+@item :after-hook
+This optional keyword specifies a single Lisp form to evaluate as the
+final act of the mode function, after the mode hooks have been run.
+It should not be quoted. Since the form might be evaluated after the
+mode function has terminated, it should not access any element of the
+mode function's local state. An @code{:after-hook} form is useful for
+setting up aspects of the mode which depend on the user's settings,
+which in turn may have been changed in a mode hook.