diff --git a/lib/simple_captcha/view.rb b/lib/simple_captcha/view.rb
index fc57080..65632fd 100644
--- a/lib/simple_captcha/view.rb
+++ b/lib/simple_captcha/view.rb
@@ -106,9 +106,9 @@ def generate_simple_captcha_data(code)
       
       def simple_captcha_key(key_name = nil)
         if key_name.nil?
-          session[:captcha] ||= SimpleCaptcha::Utils.generate_key(session[:id].to_s, 'captcha')
+          session[:captcha] ||= SimpleCaptcha::Utils.generate_key(session[:session_id].to_s, 'captcha')
         else
-          SimpleCaptcha::Utils.generate_key(session[:id].to_s, key_name)
+          SimpleCaptcha::Utils.generate_key(session[:session_id].to_s, key_name)
         end
       end 
   end