diff --git a/etc/NEWS b/etc/NEWS
index a59a1a3017d..ae267c4c5dd 100644
--- a/etc/NEWS
+++ b/etc/NEWS
@@ -184,6 +184,17 @@ accepts a comma-separated list.  The prompt format can include the
 separator description and the separator string, which are both stored as
 text properties of the 'crm-separator' regular expression.
 
+---
+*** New user option 'completion-preview-sort-function'.
+This option controls how Completion Preview mode sorts completion
+candidates.  If you use this mode together with an in-buffer completion
+popup interface, such as the interfaces that the GNU ELPA packages Corfu
+and Company provide, you can set this option to the same sort function
+that your popup interface uses for a more integrated experience.
+
+Note: 'completion-preview-sort-function' was present also in Emacs 30.1,
+albeit as a variable, not a user option.
+
 ** Windows
 
 +++
diff --git a/lisp/completion-preview.el b/lisp/completion-preview.el
index 4fc9bb0c9f3..6ccf235dbc5 100644
--- a/lisp/completion-preview.el
+++ b/lisp/completion-preview.el
@@ -226,8 +226,20 @@ affect the background color, for example with `hl-line-mode'."
                  (const :tag "Disable" nil))
   :version "31.1")
 
-(defvar completion-preview-sort-function #'minibuffer--sort-by-length-alpha
-  "Sort function to use for choosing a completion candidate to preview.")
+(defcustom completion-preview-sort-function #'minibuffer--sort-by-length-alpha
+  "Sort function to use for choosing a completion candidate to preview.
+
+Completion Preview mode calls the function that this option specifies to
+sort completion candidates.  The function takes one argument, the list
+of candidates, and returns the list sorted.
+
+The default sort function sorts first by length, then alphabetically.
+To disable sorting, set this option to `identity'.
+
+If the completion table that produces the candidates already specifies a
+sort function, it takes precedence over this option."
+  :type 'function
+  :version "31.1")
 
 (defface completion-preview
   '((t :inherit shadow))