diff --git a/modules/rosenthal/services/desktop.scm b/modules/rosenthal/services/desktop.scm
index 82b9f07..466a8a3 100644
--- a/modules/rosenthal/services/desktop.scm
+++ b/modules/rosenthal/services/desktop.scm
@@ -597,20 +597,12 @@ gtk-key-theme-name = ~a~%"
      ,(local-file "../examples/dot-config/wezterm/wezterm.lua"))
     ;; Prevent Noctalia shell initial screen.
     (".cache/noctalia/shell-state.json"
-     ,(computed-file "noctalia-shell-state.json"
-        (with-extensions (list guile-json-4)
-          #~(begin
-              (use-modules (json))
-              (call-with-output-file #$output
-                (lambda (port)
-                  (scm->json
-                   `(("changelogState"
-                      ("lastSeenVersion"
-                       . ,(string-append "v" #$(package-version noctalia-shell))))
-                     ("telemetry"
-                      ("instanceId" . "")))
-                   port
-                   #:pretty #t)))))))
+     ,(json-file "noctalia-shell-state.json"
+        #~'(("changelogState"
+             ("lastSeenVersion"
+              . #$(string-append "v" (package-version noctalia-shell))))
+            ("telemetry"
+             ("instanceId" . "")))))
     ,@%rosenthal-skeletons))
 
 
diff --git a/modules/rosenthal/utils/file.scm b/modules/rosenthal/utils/file.scm
index 5f5732d..56c293a 100644
--- a/modules/rosenthal/utils/file.scm
+++ b/modules/rosenthal/utils/file.scm
@@ -7,12 +7,14 @@
   ;; Utilities
   #:use-module (guix gexp)
   ;; Guix packages
+  #:use-module (gnu packages guile)
   #:use-module (gnu packages guile-xyz)
   #:export (computed-substitution-with-inputs
             file-content
             hidden-desktop-entry
 
             ini-file
+            json-file
             yaml-file))
 
 ;; XXX: ‘substitute*’ doesn't fully support Unicode:
@@ -67,6 +69,17 @@ format."
           (call-with-output-file #$output
             (cut scm->ini #$exp #:port <>))))))
 
+;; https://github.com/aconchillo/guile-json
+(define (json-file name exp)
+  "Return file-like object NAME, serialized from G-expression EXP in JSON
+format."
+  (computed-file name
+    (with-extensions (list guile-json-4)
+      #~(begin
+          (use-modules (srfi srfi-26) (json))
+          (call-with-output-file #$output
+            (cut scm->json #$exp <> #:pretty #t))))))
+
 ;; https://gitlab.com/yorgath/guile-yamlpp
 (define (yaml-file name exp)
   "Return file-like object NAME, serialized from G-expression EXP in YAML