diff --git a/lib/omniauth/strategies/office365.rb b/lib/omniauth/strategies/office365.rb
index e94e3b1..8767936 100644
--- a/lib/omniauth/strategies/office365.rb
+++ b/lib/omniauth/strategies/office365.rb
@@ -34,6 +34,10 @@ class Office365 < OmniAuth::Strategies::OAuth2
       def raw_info
         @raw_info ||= access_token.get(authorize_params.resource + 'Me?api-version=1.5').parsed
       end
+      
+      def callback_url
+        options[:redirect_uri] || (full_host + script_name + callback_path)
+      end
     end
   end
 end