diff --git a/capsulflask/shell_scripts/ip-dhcp-host.sh b/capsulflask/shell_scripts/ip-dhcp-host.sh
index a4ae0e0..65f496e 100755
--- a/capsulflask/shell_scripts/ip-dhcp-host.sh
+++ b/capsulflask/shell_scripts/ip-dhcp-host.sh
@@ -12,4 +12,13 @@ ipv4_address="$4"
 [ "$mac_address" = '' ] && printf 'you must set $mac_address (3rd arg)\n' && exit 1
 [ "$ipv4_address" = '' ] && printf 'you must set $ipv4_address (4th arg)\n' && exit 1
 
+# for some reason libvirt appears to remember every dhcp lease even after it has expired.
+# adding a new ip-dhcp-host will fail if there already is one with the same ip address. 
+# so we will try to delete any that already exist with that IP address just in case!
+if [ "$action" == 'add' ]; then
+  printf "trying to delete any existing (probably expired) dhcp associations for $ipv4_address..."
+  virsh net-update "$network_name" delete ip-dhcp-host "<host ip='$ipv4_address' />" --live --config || true
+fi
+
+printf "adding $mac_address --> $ipv4_address to $network_name"
 virsh net-update "$network_name" "$action" ip-dhcp-host "<host mac='$mac_address' ip='$ipv4_address' />" --live --config