diff --git a/app/views/welcome/robots.text.erb b/app/views/welcome/robots.text.erb
index 10b540935..089c8e3fb 100644
--- a/app/views/welcome/robots.text.erb
+++ b/app/views/welcome/robots.text.erb
@@ -1,10 +1,10 @@
 User-agent: *
 <% @projects.each do |p| -%>
-Disallow: /projects/<%= p.to_param %>/repository
-Disallow: /projects/<%= p.to_param %>/issues
-Disallow: /projects/<%= p.to_param %>/activity
+Disallow: <%= url_for(:controller => 'repositories', :action => :show, :id => p) %>
+Disallow: <%= url_for(project_issues_path(:project_id => p)) %>
+Disallow: <%= url_for(project_activity_path(:id => p)) %>
 <% end -%>
-Disallow: /issues/gantt
-Disallow: /issues/calendar
-Disallow: /activity
-Disallow: /search
+Disallow: <%= url_for(issues_gantt_path) %>
+Disallow: <%= url_for(issues_calendar_path) %>
+Disallow: <%= url_for(activity_path) %>
+Disallow: <%= url_for(search_path) %>
diff --git a/test/integration/welcome_test.rb b/test/integration/welcome_test.rb
index 12ec92d0c..6b370e5d4 100644
--- a/test/integration/welcome_test.rb
+++ b/test/integration/welcome_test.rb
@@ -25,6 +25,7 @@ class WelcomeTest < Redmine::IntegrationTest
     get '/robots.txt'
     assert_response :success
     assert_equal 'text/plain', @response.content_type
+    # It seems Redmine::Utils.relative_url_root does not effect on Rails 5.1.4
     assert @response.body.match(%r{^Disallow: /projects/ecookbook/issues\r?$})
   end
 end