diff --git a/dhcp/manifests/init.pp b/dhcp/manifests/init.pp
index c12b305..e1a8b1f 100644
--- a/dhcp/manifests/init.pp
+++ b/dhcp/manifests/init.pp
@@ -111,7 +111,7 @@ class dhcp::server::ldap inherits dhcp::server::common {
     exec { "generate-dhcp-conf":
 	path    => "/bin:/sbin:/usr/bin:/usr/sbin:/usr/local/bin:/usr/local/sbin",
 	command => "dhcpdump.py /etc/dhcpd.conf.in* > /etc/dhcpd.conf",
-	onlyif  => "! dhcpdump.py /etc/dhcpd.conf.in* | diff /etc/dhcpd.conf -",
+	unless  => "dhcpdump.py /etc/dhcpd.conf.in* | diff /etc/dhcpd.conf -",
 	require => [ File["/etc/dhcpd.conf.in"],
 		     File["/usr/local/sbin/dhcpdump.py"], ],
 	notify  => Service["dhcpd"],