Airodump-Ng Issues

I am following this tutorial here and I do the command "airmon-ng start wlan0" and it creates wlan0mon and displays "(mac80211 monitor mode cif enabled for phy0wlan0 on phy0wlan0mon) (mac80211 monitor mode cif disabled for phy0wlan0 on phy0wlan0)". After this I do the command "airodump-ng wlan0mon0" and it says that the resource is busy. Any help would be appreciated :)