diff --git a/network/vif-route-qubes b/network/vif-route-qubes
index d61f736..055fac0 100755
--- a/network/vif-route-qubes
+++ b/network/vif-route-qubes
@@ -134,6 +134,11 @@ if [ -n "$appvm_ip" ] && [ -n "$appvm_gw_ip" ] && [ "$appvm_ip" != "$netvm_ip" ]
     . "$dir/vif-qubes-nat.sh"
 fi
 
+case $- in
+(*e*) :;;
+(*) echo '-e not set'>&2; exit 1;;
+esac
+
 # add anti-spoofing rules before enabling the interface
 if [ "${ip}" ]; then
     # If we’ve been given a list of IP addresses, then add routes from us to