diff --git a/doc/guix.texi b/doc/guix.texi
index 78d1dd8b2a..cda940b1fa 100644
--- a/doc/guix.texi
+++ b/doc/guix.texi
@@ -22,7 +22,7 @@
 @set SUBSTITUTE-URLS https://@value{SUBSTITUTE-SERVER-1} https://@value{SUBSTITUTE-SERVER-2}
 
 @copying
-Copyright @copyright{} 2012-2022 Ludovic Courtès@*
+Copyright @copyright{} 2012-2023 Ludovic Courtès@*
 Copyright @copyright{} 2013, 2014, 2016 Andreas Enge@*
 Copyright @copyright{} 2013 Nikita Karetnikov@*
 Copyright @copyright{} 2014, 2015, 2016 Alex Kost@*
@@ -21340,17 +21340,6 @@ This gexp specifies the channels to use for the upgrade
 (@pxref{Channels}).  By default, the tip of the official @code{guix}
 channel is used.
 
-@item @code{expression} (default: @code{#f})
-This field specifies the Guile expression to use for the upgrade
-(@pxref{Invoking guix system}) as a list of symbols.  If no value is provided the
-@code{operating-system-file} field value will be used.
-
-@lisp
-(unattended-upgrade-configuration
-  (expression
-    '(@@ (guix system install) installation-os)))
-@end lisp
-
 @item @code{operating-system-file} (default: @code{"/run/current-system/configuration.scm"})
 This field specifies the operating system configuration file to use.
 The default is to reuse the config file of the current configuration.
@@ -21374,6 +21363,17 @@ Therefore, uses of @code{local-file} within @file{config.scm} will work
 as expected.  @xref{G-Expressions}, for information about
 @code{local-file} and @code{file-append}.
 
+@item @code{operating-system-expression} (default: @code{#f})
+This field specifies an expression that evaluates to the operating
+system to use for the upgrade.  If no value is provided the
+@code{operating-system-file} field value is used.
+
+@lisp
+(unattended-upgrade-configuration
+  (operating-system-expression
+    #~(@@ (guix system install) installation-os)))
+@end lisp
+
 @item @code{services-to-restart} (default: @code{'(mcron)})
 This field specifies the Shepherd services to restart when the upgrade
 completes.
diff --git a/gnu/services/admin.scm b/gnu/services/admin.scm
index ff5ceae47e..a864da25e9 100644
--- a/gnu/services/admin.scm
+++ b/gnu/services/admin.scm
@@ -1,6 +1,6 @@
 ;;; GNU Guix --- Functional package management for GNU
 ;;; Copyright © 2016 Jan Nieuwenhuizen <janneke@gnu.org>
-;;; Copyright © 2016-2022 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2016-2023 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2020 Brice Waegeneire <brice@waegenei.re>
 ;;; Copyright © 2023 Giacomo Leidi <goodoldpaul@autistici.org>
 ;;;
@@ -59,8 +59,8 @@ (define-module (gnu services admin)
             unattended-upgrade-service-type
             unattended-upgrade-configuration
             unattended-upgrade-configuration?
-            unattended-upgrade-configuration-expression
             unattended-upgrade-configuration-operating-system-file
+            unattended-upgrade-configuration-operating-system-expression
             unattended-upgrade-configuration-channels
             unattended-upgrade-configuration-schedule
             unattended-upgrade-configuration-services-to-restart
@@ -266,8 +266,8 @@ (define-record-type* <unattended-upgrade-configuration>
   unattended-upgrade-configuration?
   (operating-system-file unattended-upgrade-operating-system-file
                          (default "/run/current-system/configuration.scm"))
-  (expression           unattended-upgrade-expression
-                        (default #f))
+  (operating-system-expression unattended-upgrade-operating-system-expression
+                               (default #f))
   (schedule             unattended-upgrade-configuration-schedule
                         (default "30 01 * * 0"))
   (channels             unattended-upgrade-configuration-channels
@@ -302,11 +302,11 @@ (define config-file
     (unattended-upgrade-operating-system-file config))
 
   (define expression
-    (unattended-upgrade-expression config))
+    (unattended-upgrade-operating-system-expression config))
 
-  (define reconfigure-args
+  (define arguments
     (if expression
-        #~(list "-e" (format #t "~s" expression))
+        #~(list "-e" (object->string '#$expression))
         #~(list config-file)))
 
   (define code
@@ -348,7 +348,7 @@ (define (alarm-handler . _)
                      (report-invoke-error c)))
             (invoke #$(file-append guix "/bin/guix")
                     "time-machine" "-C" #$channels
-                    "--" "system" "reconfigure" #$@reconfigure-args)
+                    "--" "system" "reconfigure" #$@arguments)
 
             ;; 'guix system delete-generations' fails when there's no
             ;; matching generation.  Thus, catch 'invoke-error?'.