diff --git a/pkgs/servers/nosql/cassandra/update-script.nix b/pkgs/servers/nosql/cassandra/update-script.nix
index fd79d1fb43b8..73906b7a811a 100644
--- a/pkgs/servers/nosql/cassandra/update-script.nix
+++ b/pkgs/servers/nosql/cassandra/update-script.nix
@@ -6,7 +6,7 @@
 }:
 let
   inherit (lib) makeBinPath;
-  filename = lib.strings.replaceStrings [ "_" ] [ "." ] generation + ".nix";
+  filename = lib.strings.replaceStrings [ "_" ] [ "." ] generation + ".json";
   regex = lib.strings.replaceStrings [ "_" ] [ "[.]" ] generation;
 in
 writeScript "update-cassandra_${generation}" ''
@@ -34,12 +34,9 @@ writeScript "update-cassandra_${generation}" ''
   version="$(grep -E '^${regex}' <$tmp/versions | head -n 1)"
   hash="$(nix-prefetch-url "mirror://apache/cassandra/$version/apache-cassandra-$version-bin.tar.gz")"
   cat >${filename} <<EOF
-  # GENERATED BY update.sh
-  { callPackage, ... } @ args:
-  callPackage ./generic.nix (args // {
-    version = "$version";
-    sha256 = "$hash";
-    generation = "${generation}";
-  })
+  {
+    "version": "$version",
+    "sha256": "$hash"
+  }
   EOF
 ''