diff --git a/guix-data-service/web/revision/controller.scm b/guix-data-service/web/revision/controller.scm
index f19e1d7..87dd63c 100644
--- a/guix-data-service/web/revision/controller.scm
+++ b/guix-data-service/web/revision/controller.scm
@@ -395,7 +395,7 @@
          mime-types)
     ((application/json)
      (render-json
-      '((unknown_commit . ,commit-hash))
+      `((unknown_commit . ,commit-hash))
       #:code 404))
     (else
      (letpar& ((job