diff --git a/engine/schema/src/com/cloud/upgrade/dao/Upgrade412to420.java b/engine/schema/src/com/cloud/upgrade/dao/Upgrade412to420.java
index 3630c00b8dc..614cf14cafe 100644
--- a/engine/schema/src/com/cloud/upgrade/dao/Upgrade412to420.java
+++ b/engine/schema/src/com/cloud/upgrade/dao/Upgrade412to420.java
@@ -907,7 +907,6 @@ public class Upgrade412to420 implements DbUpgrade {
         Long vmwareDcId = 1L;
         Long zoneId;
         Long clusterId;
-        String clusterHypervisorType;
         boolean legacyZone;
         boolean ignoreZone;
         Long count;
@@ -929,7 +928,7 @@ public class Upgrade412to420 implements DbUpgrade {
 
             while (rs.next()) {
                 zoneId = rs.getLong("id");
-                clustersQuery = conn.prepareStatement("select id, hypervisor_type from `cloud`.`cluster` where removed is NULL AND data_center_id=?");
+                clustersQuery = conn.prepareStatement("select id from `cloud`.`cluster` where removed is NULL AND data_center_id=? AND hypervisor_type='VMware'");
                 clustersQuery.setLong(1, zoneId);
                 legacyZone = false;
                 ignoreZone = true;
@@ -943,39 +942,36 @@ public class Upgrade412to420 implements DbUpgrade {
                     dcOfPreviousCluster = null;
                     dcOfCurrentCluster = null;
                     do {
-                        clusterHypervisorType = clusters.getString("hypervisor_type");
                         clusterId = clusters.getLong("id");
-                        if (clusterHypervisorType.equalsIgnoreCase("VMware")) {
-                            ignoreZone = false;
-                            clusterDetailsQuery = conn.prepareStatement("select value from `cloud`.`cluster_details` where name='url' and cluster_id=?");
-                            clusterDetailsQuery.setLong(1, clusterId);
-                            clusterDetails = clusterDetailsQuery.executeQuery();
-                            clusterDetails.next();
-                            url = clusterDetails.getString("value");
-                            tokens = url.split("/"); // url format - http://vcenter/dc/cluster
-                            vc = tokens[2];
-                            dcName = tokens[3];
-                            dcOfPreviousCluster = dcOfCurrentCluster;
-                            dcOfCurrentCluster = dcName + "@" + vc;
-                            if (count > 0) {
-                                if (!dcOfPreviousCluster.equalsIgnoreCase(dcOfCurrentCluster)) {
-                                    legacyZone = true;
-                                    s_logger.debug("Marking the zone " + zoneId + " as legacy zone.");
-                                }
+                        ignoreZone = false;
+                        clusterDetailsQuery = conn.prepareStatement("select value from `cloud`.`cluster_details` where name='url' and cluster_id=?");
+                        clusterDetailsQuery.setLong(1, clusterId);
+                        clusterDetails = clusterDetailsQuery.executeQuery();
+                        clusterDetails.next();
+                        url = clusterDetails.getString("value");
+                        tokens = url.split("/"); // url format - http://vcenter/dc/cluster
+                        vc = tokens[2];
+                        dcName = tokens[3];
+                        dcOfPreviousCluster = dcOfCurrentCluster;
+                        dcOfCurrentCluster = dcName + "@" + vc;
+                        if (count > 0) {
+                            if (!dcOfPreviousCluster.equalsIgnoreCase(dcOfCurrentCluster)) {
+                                legacyZone = true;
+                                s_logger.debug("Marking the zone " + zoneId + " as legacy zone.");
                             }
-                        } else {
-                            s_logger.debug("Ignoring zone " + zoneId + " with hypervisor type " + clusterHypervisorType);
-                            break;
                         }
                         count++;
                     } while (clusters.next());
+
+                    // Ignore the zone without even one VMware cluster.
                     if (ignoreZone) {
-                        continue; // Ignore the zone with hypervisors other than VMware
+                        continue;
                     }
                 }
                 if (legacyZone) {
                     listOfLegacyZones.add(zoneId);
                 } else {
+                    // Associate DC with the zone.
                     assert(clusterDetails != null) : "Couldn't retrieve details of cluster!";
                     s_logger.debug("Discovered non-legacy zone " + zoneId + ". Processing the zone to associate with VMware datacenter.");