diff --git a/dhclient-script b/dhclient-script
index 6dcd40a..60363c8 100644
--- a/dhclient-script
+++ b/dhclient-script
@@ -409,10 +409,11 @@ BOUND|RENEW|REBIND|REBOOT)
   if [ x$new_interface_mtu != x ] ; then
     /sbin/ip link set $interface mtu $new_interface_mtu
   fi
-  if [ x$new_ip_address != x -a x$old_ip_address != x$new_ip_address ] || \
-     [ x$reason = xBOUND ] || [ x$reason = xREBOOT ]; then
+  if [ x$new_ip_address != x ] && \
+     [ x$new_ip_address != x$old_ip_address -o \
+       x$reason = xBOUND -o x$reason = xREBOOT ]; then
 
-    /sbin/ip addr add $new_ip_address/$new_subnet_mask \
+    /sbin/ip addr add $new_ip_address/${new_subnet_mask:-32} \
                       ${new_broadcast_arg} \
                       dev $interface
 
@@ -483,7 +484,7 @@ TIMEOUT)
 
   if [ x$new_ip_address != x -a x$old_ip_address != x$new_ip_address ];
   then
-    /sbin/ip addr add $new_ip_address/$new_subnet_mask \
+    /sbin/ip addr add $new_ip_address/${new_subnet_mask:-32} \
                       ${new_broadcast_arg} \
                       dev $interface