diff --git a/pkgs/pkgs-lib/formats.nix b/pkgs/pkgs-lib/formats.nix
index 1f63c44232f0..3576a00e9943 100644
--- a/pkgs/pkgs-lib/formats.nix
+++ b/pkgs/pkgs-lib/formats.nix
@@ -495,8 +495,7 @@ optionalAttrs allowAliases aliases
   */
   cdn =
     { }:
-    json { }
-    // {
+    {
       type = serializableValueWith { typeName = "CDN"; };
 
       generate =