diff --git a/unstack.sh b/unstack.sh
index 1bace15..49f1e8b 100755
--- a/unstack.sh
+++ b/unstack.sh
@@ -110,5 +110,6 @@
 
 # Quantum dhcp agent runs dnsmasq
 if is_service_enabled q-dhcp; then
-    sudo kill -9 $(ps aux | awk '/[d]nsmasq.+interface=tap/ { print $2 }')
+    pid=$(ps aux | awk '/[d]nsmasq.+interface=tap/ { print $2 }')
+    [ ! -z $pid ] && sudo kill -9 $pid
 fi