diff --git a/engine/schema/src/com/cloud/upgrade/dao/Upgrade440to450.java b/engine/schema/src/com/cloud/upgrade/dao/Upgrade440to450.java
index caf3b422d23..aad5162e7d2 100644
--- a/engine/schema/src/com/cloud/upgrade/dao/Upgrade440to450.java
+++ b/engine/schema/src/com/cloud/upgrade/dao/Upgrade440to450.java
@@ -22,6 +22,7 @@ import java.sql.Connection;
 import java.util.ArrayList;
 import java.util.HashMap;
 import java.util.List;
+import java.util.Map;
 
 import org.apache.log4j.Logger;
 
@@ -80,8 +81,8 @@ public class Upgrade440to450 implements DbUpgrade {
         uniqueKeys.put("storage_pool", keys);
 
         s_logger.debug("Droping id_2 key from storage_pool table");
-        for (String tableName : uniqueKeys.keySet()) {
-            DbUpgradeUtils.dropKeysIfExist(conn, tableName, uniqueKeys.get(tableName), false);
+        for (Map.Entry<String, List<String>> entry: uniqueKeys.entrySet()) {
+            DbUpgradeUtils.dropKeysIfExist(conn,entry.getKey(), entry.getValue(), false);
         }
     }
 }