WHATSAPP BACKUP! Why can't i find the backup conversation button in chat settings?

I need to backup my whatsapp convo to iCloud from my iPhone 4s, because i wanna transfer the chat history to my iPhone 5s… But somehow i can't find the "backup conversation" button in chat settings. I have alrdy downloaded the latest version of whatsapp… WHAT IS GOING WRONG?

See the procedure
http://www.freeandroidtricks.com/2014/01/how-to-backup-whatsapp-messages.html