diff --git a/puppet/zulip_ops/files/zulip-ec2-configure-interfaces b/puppet/zulip_ops/files/zulip-ec2-configure-interfaces
index 5e868e195f..f63f3566ed 100755
--- a/puppet/zulip_ops/files/zulip-ec2-configure-interfaces
+++ b/puppet/zulip_ops/files/zulip-ec2-configure-interfaces
@@ -105,7 +105,9 @@ for device in macs.values():
         # HACK: It appears on Xenial device_number in the data set is 0 but in reality it is 3
         device_number += 3
 
-    if address_of(device_number) is None:
+    address = address_of(device_number)
+
+    if address is None:
         # If the device was not autoconfigured, do so now.
         log.info("Device ens%i not configured, starting dhcpd" % (device_number,))
         subprocess.check_call(['/sbin/dhcpcd', 'ens%i' % device_number])
@@ -127,7 +129,7 @@ for device in macs.values():
             ['/sbin/iptables', '-t', 'mangle', '-A', 'OUTPUT', '-m', 'conntrack', '--ctorigdst',
              address, '-j', 'MARK', '--set-mark', dev_num])
 
-    to_configure.remove(address_of(device_number))
+    to_configure.remove(address)
 
     for (count, ip) in enumerate(to_configure):
         # Configure the IP via a virtual interface