diff --git a/config/routes.rb b/config/routes.rb
index 540f3d0af..2db1a6abf 100644
--- a/config/routes.rb
+++ b/config/routes.rb
@@ -405,7 +405,7 @@ Rails.application.routes.draw do
 
   match 'uploads', :to => 'attachments#upload', :via => :post
 
-  get 'robots', :to => 'welcome#robots'
+  get 'robots.:format', :to => 'welcome#robots', :constraints => {format: 'txt'}
 
   Redmine::Plugin.directory.glob("*/config/routes.rb").sort.each do |plugin_routes_path|
     instance_eval(plugin_routes_path.read, plugin_routes_path.to_s)
diff --git a/test/integration/welcome_test.rb b/test/integration/welcome_test.rb
index d1b0c8889..31fd57fcd 100644
--- a/test/integration/welcome_test.rb
+++ b/test/integration/welcome_test.rb
@@ -54,4 +54,11 @@ class WelcomeTest < Redmine::IntegrationTest
       assert @response.body.match(%r{^Disallow: /\r?$})
     end
   end
+
+  def test_robots_should_not_respond_to_unsupported_formats
+    %w(robots.json robots).each do |file|
+      get "/#{file}"
+      assert_response :not_found
+    end
+  end
 end