Ubuntu Airmon-ng error

i am having problem while starting airmon-ng start wlp1s0. i am using ubuntu 16.04

# airmon-ng start wlp1s0

Found 5 processes that could cause trouble.
If airodump-ng, aireplay-ng or airtun-ng stops working after a short period of time, you may want to kill (some of) them!

PID     Name
874     avahi-daemon
922     avahi-daemon
966     NetworkManager
1083    wpa_supplicant
13392   dhclient
Process with PID 13392 (dhclient) is running on interface wlp1s0

Interface   Chipset     Driver
wlp1s0      Broadcom    wl - [phy0]mon0: ERROR while getting interface flags: No such device (monitor mode enabled on mon0)

# airmon-ng
Interface   Chipset     Driver
wlp1s0      Broadcom    wl - [phy0]