diff --git a/testing/watch-port-80.sh b/testing/watch-port-80.sh
index a479496c..f57925f6 100755
--- a/testing/watch-port-80.sh
+++ b/testing/watch-port-80.sh
@@ -1,5 +1,6 @@
 #!/bin/sh
 
 PORT=${1:-"80"}
+IFACE=${2:-"any"}
 
-sudo tcpdump -i any -s0 -l -n -q -A "tcp port ${PORT} and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)"
+sudo tcpdump -i $IFACE -s0 -l -n -q -A "tcp port ${PORT} and (((ip[2:2] - ((ip[0]&0xf)<<2)) - ((tcp[12]&0xf0)>>2)) != 0)"