diff --git a/guix/scripts/system.scm b/guix/scripts/system.scm
index cdd78a7849..4ca4f1fa85 100644
--- a/guix/scripts/system.scm
+++ b/guix/scripts/system.scm
@@ -328,26 +328,25 @@ (define-syntax-rule (unless-file-not-found exp)
           #f
           (apply throw args)))))
 
+(define (generation->boot-parameters profile number)
+  "Return the 'boot-parameters' for the generation of PROFILE specified
+by NUMBER."
+  (unless-file-not-found
+   (let* ((system (generation-file-name profile number))
+          (params (read-boot-parameters-file system))
+          (epoch (stat:mtime (lstat system)))
+          (text (boot-parameters-label params)))
+     (boot-parameters
+      (inherit params)
+      (label (decorated-boot-label text number epoch))))))
+
 (define* (profile->boot-alternatives #:optional (profile %system-profile)
                                      (numbers
                                       (reverse (generation-numbers profile))))
   "Return a list of 'boot-parameters' for the generations of PROFILE specified
 by NUMBERS, which is a list of generation numbers. The list is ordered from
 the most recent to the oldest profiles."
-  (define (system->boot-parameters system number epoch)
-    (unless-file-not-found
-     (let* ((params           (read-boot-parameters-file system))
-            (text             (boot-parameters-label params)))
-       (boot-parameters
-        (inherit params)
-        (label (decorated-boot-label text number epoch))))))
-  (let* ((systems (map (cut generation-file-name profile <>)
-                       numbers))
-         (times   (map (lambda (system)
-                         (unless-file-not-found
-                          (stat:mtime (lstat system))))
-                       systems)))
-    (filter-map system->boot-parameters systems numbers times)))
+  (filter-map (cut generation->boot-parameters profile <>) numbers))
 
 
 ;;;
@@ -395,8 +394,7 @@ (define (reinstall-bootloader store number)
                              (bootloader bootloader)))
 
          ;; Make the specified system generation the default entry.
-         (params (first (profile->boot-alternatives %system-profile
-                                                    (list number))))
+         (params (generation->boot-parameters %system-profile number))
          (locale (boot-parameters-locale params))
          (store-crypto-devices (boot-parameters-store-crypto-devices params))
          (store-directory-prefix