Wireless roaming is messing up resolv.conf

Here's my wifi interfaces

#auto wlp1s0
allow-hotplug wlp1s0
iface wlp1s0 inet manual
        wpa-roam /etc/wpa_supplicant/wpa_supplicant.conf
#        up /usr/sbin/wondershaper -a wlan0 -d 9500 -u 15000
#        down /usr/sbin/wondershaper -a wlan0 -c

allow-hotplug RWB
iface RWB inet dhcp

where RWB is an AP defined in /etc/wpa_supplicant/wpa_supplicant.conf Whenever I connected to that AP the dhclient (I presume) updates the file /etc/resolv.conf. This means that when I go away from RWB and connect to something else -- including wired ethernet -- DNS fails because the IP address in resolv.conf is nolonger routable. Naive fix is to stop dhcp client from updating resolv.conf, but surely there is a conventional configuration for this situation that solves this problem -- what?