diff --git a/guix-data-service/web/render.scm b/guix-data-service/web/render.scm
index c4a8e85..02ec42d 100644
--- a/guix-data-service/web/render.scm
+++ b/guix-data-service/web/render.scm
@@ -39,6 +39,7 @@
             render-static-asset
             render-html
             scm-alist->streaming-json
+            list->json-array
             render-json
             render-text
             not-found
@@ -160,7 +161,7 @@
               (lambda (port)
                 (sxml->html sxml port)))))))
 
-(define* (scm-alist->streaming-json alist port #:key unicode)
+(define* (scm-alist->streaming-json alist port #:key (unicode #t))
   (put-string port "{")
   (pair-for-each
    (lambda (pair)
@@ -179,6 +180,16 @@
    alist)
   (put-string port "}"))
 
+(define* (list->json-array proc list port #:key (unicode #t))
+  (put-string port "[")
+  (pair-for-each
+   (lambda (pair)
+     (scm->json (proc (car pair)) port #:unicode unicode)
+     (unless (null? (cdr pair))
+       (put-string port ",")))
+   list)
+  (put-string port "]"))
+
 (define* (render-json json #:key (extra-headers '())
                       (code 200)
                       stream?)