diff --git a/server/src/com/cloud/configuration/ConfigurationManagerImpl.java b/server/src/com/cloud/configuration/ConfigurationManagerImpl.java
index d2e5aaa39a1..2e2c39faf3c 100755
--- a/server/src/com/cloud/configuration/ConfigurationManagerImpl.java
+++ b/server/src/com/cloud/configuration/ConfigurationManagerImpl.java
@@ -2666,7 +2666,7 @@ ConfigurationManagerImpl extends ManagerBase implements ConfigurationManager, Co
                 List<VlanVO> vlans = _vlanDao.listVlansByNetworkId(network.getId());
                 if (vlans != null && vlans.size() > 0) {
                     VlanVO vlan = vlans.get(0);
-                    if (vlanId == null) {
+                    if (vlanId == null || vlanId.contains(Vlan.UNTAGGED)) {
                         vlanId = vlan.getVlanTag();
                     } else if (!NetUtils.isSameIsolationId(vlan.getVlanTag(), vlanId)) {
                         throw new InvalidParameterValueException("there is already one vlan " + vlan.getVlanTag()