diff --git a/devstack/lib/dns b/devstack/lib/dns
index ff79085f7f7..aeb928c1a7d 100644
--- a/devstack/lib/dns
+++ b/devstack/lib/dns
@@ -1,5 +1,5 @@
 function configure_dns_extension {
-    enable_ml2_extension_driver "dns"
+    neutron_ml2_extension_driver_add "dns"
 }
 function post_config_dns_extension {
     iniset $NEUTRON_CONF DEFAULT dns_domain openstackgate.local
diff --git a/devstack/lib/ml2 b/devstack/lib/ml2
index 057d445ea38..3dde13ec091 100644
--- a/devstack/lib/ml2
+++ b/devstack/lib/ml2
@@ -1,18 +1,8 @@
 source $LIBDIR/ml2_drivers/sriovnicswitch
 
 
-function enable_ml2_extension_driver {
-    local extension_driver=$1
-    if [[ -z "$Q_ML2_PLUGIN_EXT_DRIVERS" ]]; then
-        Q_ML2_PLUGIN_EXT_DRIVERS=$extension_driver
-    elif [[ ! ,${Q_ML2_PLUGIN_EXT_DRIVERS}, =~ ,${extension_driver}, ]]; then
-        Q_ML2_PLUGIN_EXT_DRIVERS+=",$extension_driver"
-    fi
-}
-
-
 function configure_qos_ml2 {
-    enable_ml2_extension_driver "qos"
+    neutron_ml2_extension_driver_add "qos"
 }
 
 
@@ -26,4 +16,4 @@ function configure_ml2 {
             configure_ml2_$mechanism_driver
         fi
     done
-}
\ No newline at end of file
+}