diff --git a/.config/guix/system/default.scm b/.config/guix/system/default.scm
index 52df4f04..fac48484 100644
--- a/.config/guix/system/default.scm
+++ b/.config/guix/system/default.scm
@@ -58,30 +58,32 @@ StrictNodes 1")
    (service tor-service-type
             (tor-configuration
              (config-file (plain-file "tor.conf" %ambrevar/tor-config))))
-  ;; Use the "desktop" services, which include the X11 log-in service, networking
-  ;; with Wicd, and more.
-  (modify-services
-      %desktop-services
-    ;; (guix-service-type config =>
-    ;;                    (guix-configuration
-    ;;                     (inherit config)
-    ;;                     ;; Don't clean build deps.
-    ;;                     ;; See (info "(guix) Invoking guix-daemon").
-    ;;                     ;; WARNING: This tends to yield an ever-growing store.
-    ;;                     ;; (extra-options '("--gc-keep-outputs"))
-    ;;                     ;; Specify substitutes manually.  Defaults
-    ;;                     ;; should be good enough in most cases.
-    ;;                     (substitute-urls
-    ;;                      (list
-    ;;                       "https://ci.guix.gnu.org"
-    ;;                       "https://gx.bufio.org"))
-    ;;                     (extra-options '("--max-jobs=2"))))
-    (udev-service-type config =>
-                       (udev-configuration
-                        (inherit config)
-                        (rules (append (udev-configuration-rules config)
-                                       (list ;; %nitrokey-udev-rule
-                                        %ambrevar/cdemu-vhba-udev-rule))))))))
+   ;; Use the "desktop" services, which include the X11 log-in service, networking
+   ;; with Wicd, and more.
+   (modify-services
+       %desktop-services
+     (guix-service-type config =>
+                        (guix-configuration
+                         (inherit config)
+                         ;; Don't clean build deps.
+                         ;; See (info "(guix) Invoking guix-daemon").
+                         ;; WARNING: This tends to yield an ever-growing store.
+                         ;; (extra-options '("--gc-keep-outputs"))
+                         (substitute-urls (append
+                                           (@@ (guix scripts substitute) %default-substitute-urls)
+                                           ;; TODO: Does not work?
+                                           ;; Nonguix:
+                                           (list "https://mirror.brielmaier.net")))
+                         (authorized-keys (append
+                                           %default-authorized-guix-keys
+                                           (list (local-file
+                                                  (format #f "~a/.config/guix/mirror.brielmaier.net.pub" (getenv "HOME"))))))))
+     (udev-service-type config =>
+                        (udev-configuration
+                         (inherit config)
+                         (rules (append (udev-configuration-rules config)
+                                        (list ;; %nitrokey-udev-rule
+                                         %ambrevar/cdemu-vhba-udev-rule))))))))
 
 (define-public %ambrevar/packages
   (cons* nss-certs          ; for HTTPS access