diff --git a/dhcp/files/dhcpdump.py b/dhcp/files/dhcpdump.py
index d4506ba..e691111 100755
--- a/dhcp/files/dhcpdump.py
+++ b/dhcp/files/dhcpdump.py
@@ -24,7 +24,7 @@ def main():
 
 
 def ldapsearch(filter):
-    p = Popen(['ldapsearch', '-x', '-z', '0', '-LLL', filter, 'cn', 'macAddress', 'ipHostNumber'],
+    p = Popen(['ldapsearch', '-x', '-z', '0', '-S', 'cn', '-LLL', filter, 'cn', 'macAddress', 'ipHostNumber'],
                bufsize=1024, stdout=PIPE, close_fds=True)
     ret = []
     cur = {}