diff --git a/gnu/build/activation.scm b/gnu/build/activation.scm
index 0e77677de1..820e04d648 100644
--- a/gnu/build/activation.scm
+++ b/gnu/build/activation.scm
@@ -1,5 +1,5 @@
 ;;; GNU Guix --- Functional package management for GNU
-;;; Copyright © 2013, 2014, 2015, 2016, 2017, 2018 Ludovic Courtès <ludo@gnu.org>
+;;; Copyright © 2013, 2014, 2015, 2016, 2017, 2018, 2019 Ludovic Courtès <ludo@gnu.org>
 ;;; Copyright © 2015 Mark H Weaver <mhw@netris.org>
 ;;;
 ;;; This file is part of GNU Guix.
@@ -18,6 +18,7 @@
 ;;; along with GNU Guix.  If not, see <http://www.gnu.org/licenses/>.
 
 (define-module (gnu build activation)
+  #:use-module (gnu system accounts)
   #:use-module (gnu build linux-boot)
   #:use-module (guix build utils)
   #:use-module (ice-9 ftw)
@@ -212,37 +213,42 @@ logged in."
       (apply add-user name group rest)))
 
 (define (activate-users+groups users groups)
-  "Make sure the accounts listed in USERS and the user groups listed in GROUPS
-are all available.
-
-Each item in USERS is a list of all the characteristics of a user account;
-each item in GROUPS is a tuple with the group name, group password or #f, and
-numeric gid or #f."
+  "Make sure USERS (a list of user account records) and GROUPS (a list of user
+group records) are all available."
   (define (touch file)
     (close-port (open-file file "a0b")))
 
   (define activate-user
-    (match-lambda
-     ((name uid group supplementary-groups comment home create-home?
-       shell password system?)
-      (let ((profile-dir (string-append "/var/guix/profiles/per-user/"
-                                        name)))
-        (ensure-user name group
-                     #:uid uid
-                     #:system? system?
-                     #:supplementary-groups supplementary-groups
-                     #:comment comment
-                     #:home home
-                     #:create-home? create-home?
+    (lambda (user)
+      (let ((name         (user-account-name user))
+            (uid          (user-account-uid user))
+            (group        (user-account-group user))
+            (supplementary-groups
+             (user-account-supplementary-groups user))
+            (comment      (user-account-comment user))
+            (home         (user-account-home-directory user))
+            (create-home? (user-account-create-home-directory? user))
+            (shell        (user-account-shell user))
+            (password     (user-account-password user))
+            (system?      (user-account-system? user)))
+        (let ((profile-dir (string-append "/var/guix/profiles/per-user/"
+                                          name)))
+          (ensure-user name group
+                       #:uid uid
+                       #:system? system?
+                       #:supplementary-groups supplementary-groups
+                       #:comment comment
+                       #:home home
+                       #:create-home? create-home?
 
-                     #:shell shell
-                     #:password password)
+                       #:shell shell
+                       #:password password)
 
-        (unless system?
-          ;; Create the profile directory for the new account.
-          (let ((pw (getpwnam name)))
-            (mkdir-p profile-dir)
-            (chown profile-dir (passwd:uid pw) (passwd:gid pw))))))))
+          (unless system?
+            ;; Create the profile directory for the new account.
+            (let ((pw (getpwnam name)))
+              (mkdir-p profile-dir)
+              (chown profile-dir (passwd:uid pw) (passwd:gid pw))))))))
 
   ;; 'groupadd' aborts if the file doesn't already exist.
   (touch "/etc/group")
@@ -251,18 +257,18 @@ numeric gid or #f."
   (mkdir-p "/var/lib")
 
   ;; Create the root account so we can use 'useradd' and 'groupadd'.
-  (activate-user (find (match-lambda
-                        ((name (? zero?) _ ...) #t)
-                        (_ #f))
-                       users))
+  (activate-user (find (compose zero? user-account-uid) users))
 
   ;; Then create the groups.
-  (for-each (match-lambda
-             ((name password gid system?)
-              (unless (false-if-exception (getgrnam name))
-                (add-group name
-                           #:gid gid #:password password
-                           #:system? system?))))
+  (for-each (lambda (group)
+              (let ((name     (user-group-name group))
+                    (password (user-group-password group))
+                    (gid      (user-group-id group))
+                    (system?  (user-group-system? group)))
+                (unless (false-if-exception (getgrnam name))
+                  (add-group name
+                             #:gid gid #:password password
+                             #:system? system?))))
             groups)
 
   ;; Create the other user accounts.
@@ -272,35 +278,33 @@ numeric gid or #f."
   (for-each delete-user
             (lset-difference string=?
                              (map passwd:name (current-users))
-                             (match users
-                               (((names . _) ...)
-                                names))))
+                             (map user-account-name users)))
   (for-each delete-group
             (lset-difference string=?
                              (map group:name (current-groups))
-                             (match groups
-                               (((names . _) ...)
-                                names)))))
+                             (map user-group-name groups))))
 
 (define (activate-user-home users)
   "Create and populate the home directory of USERS, a list of tuples, unless
 they already exist."
   (define ensure-user-home
-    (match-lambda
-      ((name uid group supplementary-groups comment home create-home?
-             shell password system?)
-       ;; The home directories of system accounts are created during
-       ;; activation, not here.
-       (unless (or (not home) (not create-home?) system?
-                   (directory-exists? home))
-         (let* ((pw  (getpwnam name))
-                (uid (passwd:uid pw))
-                (gid (passwd:gid pw)))
-           (mkdir-p home)
-           (chown home uid gid)
-           (unless system?
-             (copy-account-skeletons home
-                                     #:uid uid #:gid gid)))))))
+    (lambda (user)
+      (let ((name         (user-account-name user))
+            (home         (user-account-home-directory user))
+            (create-home? (user-account-create-home-directory? user))
+            (system?      (user-account-system? user)))
+        ;; The home directories of system accounts are created during
+        ;; activation, not here.
+        (unless (or (not home) (not create-home?) system?
+                    (directory-exists? home))
+          (let* ((pw  (getpwnam name))
+                 (uid (passwd:uid pw))
+                 (gid (passwd:gid pw)))
+            (mkdir-p home)
+            (chown home uid gid)
+            (unless system?
+              (copy-account-skeletons home
+                                      #:uid uid #:gid gid)))))))
 
   (for-each ensure-user-home users))
 
diff --git a/gnu/system/accounts.scm b/gnu/system/accounts.scm
index 36ee62e851..eb18fb5e43 100644
--- a/gnu/system/accounts.scm
+++ b/gnu/system/accounts.scm
@@ -18,6 +18,7 @@
 
 (define-module (gnu system accounts)
   #:use-module (guix records)
+  #:use-module (ice-9 match)
   #:export (user-account
             user-account?
             user-account-name
@@ -38,6 +39,9 @@
             user-group-id
             user-group-system?
 
+            sexp->user-account
+            sexp->user-group
+
             default-shell))
 
 
@@ -79,3 +83,27 @@
   (id             user-group-id (default #f))
   (system?        user-group-system?              ; Boolean
                   (default #f)))
+
+(define (sexp->user-group sexp)
+  "Take SEXP, a tuple as returned by 'user-group->gexp', and turn it into a
+user-group record."
+  (match sexp
+    ((name password id system?)
+     (user-group (name name)
+                 (password password)
+                 (id id)
+                 (system? system?)))))
+
+(define (sexp->user-account sexp)
+  "Take SEXP, a tuple as returned by 'user-account->gexp', and turn it into a
+user-account record."
+  (match sexp
+    ((name uid group supplementary-groups comment home-directory
+           create-home-directory? shell password system?)
+     (user-account (name name) (uid uid) (group group)
+                   (supplementary-groups supplementary-groups)
+                   (comment comment)
+                   (home-directory home-directory)
+                   (create-home-directory? create-home-directory?)
+                   (shell shell) (password password)
+                   (system? system?)))))
diff --git a/gnu/system/shadow.scm b/gnu/system/shadow.scm
index a9a4afd414..4e5b6ae5f2 100644
--- a/gnu/system/shadow.scm
+++ b/gnu/system/shadow.scm
@@ -298,11 +298,14 @@ group."
   (assert-valid-users/groups accounts groups)
 
   ;; Add users and user groups.
-  #~(begin
-      (setenv "PATH"
-              (string-append #$(@ (gnu packages admin) shadow) "/sbin"))
-      (activate-users+groups (list #$@user-specs)
-                             (list #$@group-specs))))
+  (with-imported-modules (source-module-closure '((gnu system accounts)))
+    #~(begin
+        (use-modules (gnu system accounts))
+
+        (setenv "PATH"
+                (string-append #$(@ (gnu packages admin) shadow) "/sbin"))
+        (activate-users+groups (map sexp->user-account (list #$@user-specs))
+                               (map sexp->user-group (list #$@group-specs))))))
 
 (define (account-shepherd-service accounts+groups)
   "Return a Shepherd service that creates the home directories for the user
@@ -322,12 +325,15 @@ accounts among ACCOUNTS+GROUPS."
   (list (shepherd-service
          (requirement '(file-systems))
          (provision '(user-homes))
-         (modules '((gnu build activation)))
+         (modules '((gnu build activation)
+                    (gnu system accounts)))
          (start (with-imported-modules (source-module-closure
-                                        '((gnu build activation)))
+                                        '((gnu build activation)
+                                          (gnu system accounts)))
                   #~(lambda ()
                       (activate-user-home
-                       (list #$@(map user-account->gexp accounts)))
+                       (map sexp->user-account
+                            (list #$@(map user-account->gexp accounts))))
                       #f)))                       ;stop
          (stop #~(const #f))
          (respawn? #f)
