diff --git a/lib/sso_login_box/login_tag.rb b/lib/sso_login_box/login_tag.rb
index 3dd3615..7eaf0b2 100644
--- a/lib/sso_login_box/login_tag.rb
+++ b/lib/sso_login_box/login_tag.rb
@@ -6,7 +6,7 @@ module SsoLoginBox::LoginTag
       }
     </style>
     <div class=\"pull-right\">
-      <button class=\"login-btn\">
+      <button class=\"login-btn\" type=\"button\">
         <a class=\"sso_login_button\" href=\"https://api.ntnu.edu.tw/NtnuCloud/auth?response_type=#{ENV['RESPONSE_TYPE']}&client_id=#{ENV['APP_ID']}&redirect_uri=#{ENV['REDIRECT_URI']}\">
           NTNU SSO Login
         </a>