diff --git a/src/invidious/helpers/serialized_yt_data.cr b/src/invidious/helpers/serialized_yt_data.cr
index 61356555..a9798f0c 100644
--- a/src/invidious/helpers/serialized_yt_data.cr
+++ b/src/invidious/helpers/serialized_yt_data.cr
@@ -237,8 +237,15 @@ class Category
 
   def to_json(locale, json : JSON::Builder)
     json.object do
+      json.field "type", "category"
       json.field "title", self.title
-      json.field "contents", self.contents
+      json.field "contents" do
+        json.array do
+          self.contents.each do |item|
+            item.to_json(locale, json)
+          end
+        end
+      end
     end
   end