diff --git a/app/controllers/application_controller.rb b/app/controllers/application_controller.rb
index e11faaab7..f1b7f6656 100644
--- a/app/controllers/application_controller.rb
+++ b/app/controllers/application_controller.rb
@@ -30,7 +30,10 @@ class ApplicationController < ActionController::Base
   before_action :accept_terms, if: :logged_in?
 
   def render_not_found
-    render template: 'errors/not_found', layout: false, status: :not_found
+    respond_to do |format|
+      format.html { render template: 'errors/not_found', layout: false, status: :not_found }
+      format.all { head :not_found }
+    end
   end
 
   protected
diff --git a/spec/controllers/application_controller_spec.rb b/spec/controllers/application_controller_spec.rb
new file mode 100644
index 000000000..2f8e24981
--- /dev/null
+++ b/spec/controllers/application_controller_spec.rb
@@ -0,0 +1,31 @@
+RSpec.describe ApplicationController do
+  describe '#render_not_found' do
+    controller do
+      def index
+        raise ActiveRecord::RecordNotFound
+      end
+    end
+
+    context 'with HTML format' do
+      before do
+        get :index, format: :html
+      end
+
+      it 'renders the not_found template' do
+        expect(response.status).to eq(404)
+        expect(response).not_to be_redirect
+      end
+    end
+
+    context 'with JSON format' do
+      before do
+        get :index, format: :json
+      end
+
+      it 'returns empty 404 response' do
+        expect(response.status).to eq(404)
+        expect(response.body).to be_empty
+      end
+    end
+  end
+end