diff --git a/app/models/topic_list.rb b/app/models/topic_list.rb
index 1071f573741..6061747eee5 100644
--- a/app/models/topic_list.rb
+++ b/app/models/topic_list.rb
@@ -78,7 +78,7 @@ class TopicList
 
   def categories
     @categories ||=
-      topics.map { |t| [t.category, t.category&.parent_category] }.uniq.flatten.compact
+      topics.map { |t| [t.category&.parent_category, t.category] }.uniq.flatten.compact
   end
 
   def load_topics
diff --git a/spec/requests/list_controller_spec.rb b/spec/requests/list_controller_spec.rb
index 0565cd53a03..db9d9f02c66 100644
--- a/spec/requests/list_controller_spec.rb
+++ b/spec/requests/list_controller_spec.rb
@@ -239,9 +239,9 @@ RSpec.describe ListController do
         expect(response.parsed_body["topic_list"]["topics"].length).to eq(1)
         expect(response.parsed_body["topic_list"]["topics"][0]["id"]).to eq(topic.id)
         expect(response.parsed_body["topic_list"]["categories"].length).to eq(2)
-        expect(
-          response.parsed_body["topic_list"]["categories"].map { |c| c["id"] },
-        ).to contain_exactly(category.id, subcategory.id)
+        expect(response.parsed_body["topic_list"]["categories"].map { |c| c["id"] }).to eq(
+          [category.id, subcategory.id],
+        )
       end
 
       it "does not return categories if not true" do