diff --git a/lib/omniauth/strategies/mailchimp.rb b/lib/omniauth/strategies/mailchimp.rb
index 013931d..3fbfdb6 100644
--- a/lib/omniauth/strategies/mailchimp.rb
+++ b/lib/omniauth/strategies/mailchimp.rb
@@ -10,7 +10,12 @@ class Mailchimp < OmniAuth::Strategies::OAuth2
       option :client_options, {
         :site => "https://login.mailchimp.com",
         :authorize_url => '/oauth2/authorize',
-        :token_url => '/oauth2/token'
+        :token_url => '/oauth2/token',
+        :auth_scheme => :request_body
+      }
+
+      option :auth_token_params, {
+        :expires_at => 100.years.from_now
       }
 
       def request_phase