diff --git a/run/root/iptable.sh b/run/root/iptable.sh
index fbf01e2..04a3cad 100644
--- a/run/root/iptable.sh
+++ b/run/root/iptable.sh
@@ -8,7 +8,7 @@ fi
 # identify docker bridge interface name by looking at routing to
 # vpn provider remote endpoint (first ip address from name 
 # lookup in /root/start.sh)
-docker_interface=$(ip route show to match "${remote_dns_answer_first}" | grep -P -o -m 1 '[a-zA-Z0-9]+\s?+$')
+docker_interface=$(ip route show to match "${remote_dns_answer_first}" | grep -P -o -m 1 '[a-zA-Z0-9]+\s?+$' | tr -d '[:space:]')
 if [[ "${DEBUG}" == "true" ]]; then
 	echo "[debug] Docker interface defined as ${docker_interface}"
 fi