diff --git a/server/src/com/cloud/configuration/ConfigurationManagerImpl.java b/server/src/com/cloud/configuration/ConfigurationManagerImpl.java
index 75e0a37c196..2ba6ac1ae97 100755
--- a/server/src/com/cloud/configuration/ConfigurationManagerImpl.java
+++ b/server/src/com/cloud/configuration/ConfigurationManagerImpl.java
@@ -37,6 +37,8 @@ import javax.ejb.Local;
 import javax.inject.Inject;
 import javax.naming.ConfigurationException;
 
+import org.apache.log4j.Logger;
+
 import org.apache.cloudstack.acl.SecurityChecker;
 import org.apache.cloudstack.affinity.AffinityGroup;
 import org.apache.cloudstack.affinity.AffinityGroupService;
@@ -84,7 +86,6 @@ import org.apache.cloudstack.region.dao.RegionDao;
 import org.apache.cloudstack.storage.datastore.db.PrimaryDataStoreDao;
 import org.apache.cloudstack.storage.datastore.db.StoragePoolDetailsDao;
 import org.apache.cloudstack.storage.datastore.db.StoragePoolVO;
-import org.apache.log4j.Logger;
 
 import com.cloud.alert.AlertManager;
 import com.cloud.api.ApiDBUtils;
@@ -2347,6 +2348,10 @@ public class ConfigurationManagerImpl extends ManagerBase implements Configurati
             throw new InvalidParameterValueException("Disksize is required for a non-customized disk offering");
         }
 
+        if (isCustomized && numGibibytes != null) {
+            throw new InvalidParameterValueException("Disksize is not allowed for a customized disk offering");
+        }
+
         boolean localStorageRequired = false;
         String storageType = cmd.getStorageType();
         if (storageType != null) {