diff --git a/backend/app/controllers/gekanator_games_controller.rb b/backend/app/controllers/gekanator_games_controller.rb
index abc9c16..9dba4a3 100644
--- a/backend/app/controllers/gekanator_games_controller.rb
+++ b/backend/app/controllers/gekanator_games_controller.rb
@@ -2,16 +2,22 @@ class GekanatorGamesController < ApplicationController
   def create
     return head :unauthorized unless current_user
 
+    guessed_post_id = params.require(:guessed_post_id)
+    correct_post_id = params[:correct_post_id].presence
     answers = params.require(:answers).as_json
 
-    game = GekanatorGame.create!(
+    game = GekanatorGame.new(
         user: current_user,
-        guessed_post_id: params.require(:guessed_post_id),
-        correct_post_id: params[:correct_post_id].presence,
-        won: params[:guessed_post_id].to_i == params[:correct_post_id].to_i,
+        guessed_post_id:,
+        correct_post_id:,
+        won: correct_post_id.present? && guessed_post_id.to_i == correct_post_id.to_i,
         question_count: params.require(:question_count),
         answers:)
 
-    render json: { id: game.id }, status: :created
+    if game.save
+      render json: { id: game.id }, status: :created
+    else
+      render json: { errors: game.errors.full_messages }, status: :unprocessable_entity
+    end
   end
 end
diff --git a/backend/app/models/gekanator_game.rb b/backend/app/models/gekanator_game.rb
index dad5819..2808be4 100644
--- a/backend/app/models/gekanator_game.rb
+++ b/backend/app/models/gekanator_game.rb
@@ -1,10 +1,9 @@
 class GekanatorGame < ApplicationRecord
-  belongs_to :user, optional: true
+  belongs_to :user
   belongs_to :guessed_post, class_name: 'Post'
-  belongs_to :correct_post, class_name: 'Post', optional: true
+  belongs_to :correct_post, class_name: 'Post'
 
   validates :answers, presence: true
-  validates :correct_post, presence: true
   validates :question_count, numericality: { greater_than_or_equal_to: 0 }
   validates :won, inclusion: { in: [true, false] }
 end
diff --git a/backend/db/migrate/20260608000000_require_gekanator_game_user_and_correct_post.rb b/backend/db/migrate/20260608000000_require_gekanator_game_user_and_correct_post.rb
new file mode 100644
index 0000000..8071fab
--- /dev/null
+++ b/backend/db/migrate/20260608000000_require_gekanator_game_user_and_correct_post.rb
@@ -0,0 +1,17 @@
+class RequireGekanatorGameUserAndCorrectPost < ActiveRecord::Migration[8.0]
+  def up
+    execute <<~SQL.squish
+      UPDATE gekanator_games
+      SET correct_post_id = guessed_post_id
+      WHERE correct_post_id IS NULL
+    SQL
+
+    change_column_null :gekanator_games, :user_id, false
+    change_column_null :gekanator_games, :correct_post_id, false
+  end
+
+  def down
+    change_column_null :gekanator_games, :correct_post_id, true
+    change_column_null :gekanator_games, :user_id, true
+  end
+end
diff --git a/backend/db/schema.rb b/backend/db/schema.rb
index d08bd31..3ef8127 100644
--- a/backend/db/schema.rb
+++ b/backend/db/schema.rb
@@ -10,7 +10,7 @@
 #
 # It's strongly recommended that you check this file into your version control system.
 
-ActiveRecord::Schema[8.0].define(version: 2026_06_07_000000) do
+ActiveRecord::Schema[8.0].define(version: 2026_06_08_000000) do
   create_table "active_storage_attachments", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
     t.string "name", null: false
     t.string "record_type", null: false
@@ -49,9 +49,9 @@ ActiveRecord::Schema[8.0].define(version: 2026_06_07_000000) do
   end
 
   create_table "gekanator_games", charset: "utf8mb4", collation: "utf8mb4_0900_ai_ci", force: :cascade do |t|
-    t.bigint "user_id"
+    t.bigint "user_id", null: false
     t.bigint "guessed_post_id", null: false
-    t.bigint "correct_post_id"
+    t.bigint "correct_post_id", null: false
     t.boolean "won", null: false
     t.integer "question_count", null: false
     t.json "answers", null: false