diff --git a/app/views/sudo_mode/new.html.erb b/app/views/sudo_mode/new.html.erb
index dee9716..323a455 100644
--- a/app/views/sudo_mode/new.html.erb
+++ b/app/views/sudo_mode/new.html.erb
@@ -1,5 +1,5 @@
 <h2><%= l :label_password_required %></h2>
-<%= form_tag({}, class: 'tabular', id: 'sudo-form') do %>
+<%= form_tag({}, method: :post, class: 'tabular', id: 'sudo-form') do %>
 
   <%= hidden_field_tag '_method', request.request_method %>
   <%= hash_to_hidden_fields @sudo_form.original_fields %>
diff --git a/lib/redmine/sudo_mode.rb b/lib/redmine/sudo_mode.rb
index d4f2660..c853100 100644
--- a/lib/redmine/sudo_mode.rb
+++ b/lib/redmine/sudo_mode.rb
@@ -90,7 +90,7 @@ module Redmine
         return true if SudoMode.active?
 
         if param_names.blank?
-          param_names = params.keys - %w(id action controller sudo_password)
+          param_names = params.keys - %w(id action controller sudo_password _method authenticity_token utf8)
         end
 
         process_sudo_form