diff --git a/app.rb b/app.rb
index b3f33f7..5eaad3d 100644
--- a/app.rb
+++ b/app.rb
@@ -2,6 +2,7 @@
 require 'koala'
 
 enable :sessions
+set :session_secret, ENV['SESSION_KEY'] || 'a super secret session key'
 set :raise_errors, false
 set :show_exceptions, false