diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/orders/daos/HoursGroupDAO.java b/navalplanner-business/src/main/java/org/navalplanner/business/orders/daos/HoursGroupDAO.java
index cd263819e..4df24e2bc 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/orders/daos/HoursGroupDAO.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/orders/daos/HoursGroupDAO.java
@@ -20,6 +20,10 @@
 
 package org.navalplanner.business.orders.daos;
 
+import java.util.HashMap;
+import java.util.List;
+import java.util.Map;
+
 import org.apache.commons.lang.Validate;
 import org.hibernate.Criteria;
 import org.hibernate.HibernateException;
@@ -27,6 +31,7 @@ import org.hibernate.criterion.Restrictions;
 import org.navalplanner.business.common.daos.IntegrationEntityDAO;
 import org.navalplanner.business.common.exceptions.InstanceNotFoundException;
 import org.navalplanner.business.orders.entities.HoursGroup;
+import org.navalplanner.business.orders.entities.Order;
 import org.springframework.beans.factory.config.BeanDefinition;
 import org.springframework.context.annotation.Scope;
 import org.springframework.stereotype.Repository;
@@ -88,4 +93,37 @@ public class HoursGroupDAO extends IntegrationEntityDAO<HoursGroup>
         }
     }
 
-}
\ No newline at end of file
+    @Override
+    @Transactional(readOnly= true, propagation = Propagation.REQUIRES_NEW)
+    public HoursGroup findRepeatedHoursGroupCodeInDB(List<HoursGroup> hoursGroupList) {
+        final Map<String, HoursGroup> hoursGroups = createMapByCode(hoursGroupList);
+        final Map<String, HoursGroup> hoursGroupsInDB = createMapByCode(getAll());
+
+        for (String code : hoursGroups.keySet()) {
+            HoursGroup hoursGroup = hoursGroups.get(code);
+            HoursGroup hoursGroupInDB = hoursGroupsInDB.get(code);
+
+            // There's an element in the DB with the same code and it's a
+            // different element
+            if (hoursGroupInDB != null
+                    && !hoursGroupInDB.getId().equals(hoursGroup.getId())) {
+                return hoursGroup;
+            }
+        }
+        return null;
+    }
+
+    private List<HoursGroup> getAll() {
+        return list(HoursGroup.class);
+    }
+
+    private Map<String, HoursGroup> createMapByCode(List<HoursGroup> hoursGroups) {
+        Map<String, HoursGroup> result = new HashMap<String, HoursGroup>();
+        for (HoursGroup each: hoursGroups) {
+            final String code = each.getCode();
+            result.put(code, each);
+        }
+        return result;
+    }
+
+}
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/orders/daos/IHoursGroupDAO.java b/navalplanner-business/src/main/java/org/navalplanner/business/orders/daos/IHoursGroupDAO.java
index f061fa8ad..58bb9f43b 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/orders/daos/IHoursGroupDAO.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/orders/daos/IHoursGroupDAO.java
@@ -21,6 +21,9 @@
 package org.navalplanner.business.orders.daos;
 
 import org.navalplanner.business.common.daos.IIntegrationEntityDAO;
+import java.util.List;
+
+import org.navalplanner.business.common.daos.IGenericDAO;
 import org.navalplanner.business.common.exceptions.InstanceNotFoundException;
 import org.navalplanner.business.orders.entities.HoursGroup;
 
@@ -28,6 +31,7 @@ import org.navalplanner.business.orders.entities.HoursGroup;
  * Contract for {@link HoursGroupDAO}
  *
  * @author Manuel Rego Casasnovas <mrego@igalia.com>
+ * @author Diego Pino Garcia <dpino@igalia.com>
  */
 public interface IHoursGroupDAO extends IIntegrationEntityDAO<HoursGroup> {
 
@@ -36,4 +40,12 @@ public interface IHoursGroupDAO extends IIntegrationEntityDAO<HoursGroup> {
     HoursGroup findUniqueByCodeAnotherTransaction(HoursGroup hoursGroup)
             throws InstanceNotFoundException;
 
+    /**
+     * Checks if there's another {@link HoursGroup} in DB which code is the same as
+     * some of the ones in order.hoursGroups
+     *
+     * @param order
+     * @return
+     */
+    HoursGroup findRepeatedHoursGroupCodeInDB(List<HoursGroup> hoursGroupList);
 }
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/orders/entities/HoursGroup.java b/navalplanner-business/src/main/java/org/navalplanner/business/orders/entities/HoursGroup.java
index caa77ff8c..51033b663 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/orders/entities/HoursGroup.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/orders/entities/HoursGroup.java
@@ -33,7 +33,6 @@ import java.util.UUID;
 import org.apache.commons.lang.Validate;
 import org.apache.commons.logging.Log;
 import org.apache.commons.logging.LogFactory;
-import org.hibernate.validator.AssertTrue;
 import org.hibernate.validator.NotEmpty;
 import org.hibernate.validator.NotNull;
 import org.hibernate.validator.Valid;
@@ -42,6 +41,7 @@ import org.navalplanner.business.common.Registry;
 import org.navalplanner.business.common.daos.IIntegrationEntityDAO;
 import org.navalplanner.business.common.exceptions.InstanceNotFoundException;
 import org.navalplanner.business.orders.daos.IHoursGroupDAO;
+import org.navalplanner.business.common.BaseEntity;
 import org.navalplanner.business.requirements.entities.CriterionRequirement;
 import org.navalplanner.business.requirements.entities.DirectCriterionRequirement;
 import org.navalplanner.business.requirements.entities.IndirectCriterionRequirement;
@@ -396,27 +396,6 @@ public class HoursGroup extends IntegrationEntity implements Cloneable,
         return false;
     }
 
-    @AssertTrue(message = "hours group code is already being used")
-    public boolean checkConstraintUniqueCode() {
-        if (code == null) {
-            LOG.warn("Hours group code is null. "
-                    + "Not checking unique code since it would fail");
-            return true;
-        }
-        IHoursGroupDAO hoursGroupDAO = Registry.getHoursGroupDAO();
-        if (isNewObject()) {
-            return !hoursGroupDAO.existsByCodeAnotherTransaction(this);
-        } else {
-            try {
-                HoursGroup hoursGroup = hoursGroupDAO
-                        .findUniqueByCodeAnotherTransaction(this);
-                return hoursGroup.getId().equals(getId());
-            } catch (InstanceNotFoundException e) {
-                return true;
-            }
-        }
-    }
-
     public OrderLineTemplate getOrderLineTemplate() {
         return orderLineTemplate;
     }
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/orders/entities/Order.java b/navalplanner-business/src/main/java/org/navalplanner/business/orders/entities/Order.java
index 29d323345..9c1bbef59 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/orders/entities/Order.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/orders/entities/Order.java
@@ -451,19 +451,20 @@ public class Order extends OrderLineGroup {
         }
     }
 
-    @AssertTrue(message = "some code is repeated between hours group codes")
-    public boolean checkConstraintHoursGroupCodeNotRepeated() {
+    public HoursGroup findRepeatedHoursGroupCode() {
         Set<String> codes = new HashSet<String>();
 
         for (HoursGroup hoursGroup : getHoursGroups()) {
             String code = hoursGroup.getCode();
-            if (codes.contains(code)) {
-                return false;
+            if (code != null) {
+                if (codes.contains(code)) {
+                    return hoursGroup;
+                }
+                codes.add(code);
             }
-            codes.add(code);
         }
 
-        return true;
+        return null;
     }
 
     @Override
diff --git a/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/OrderModel.java b/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/OrderModel.java
index ba76de3bf..f5fcc1dfb 100644
--- a/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/OrderModel.java
+++ b/navalplanner-webapp/src/main/java/org/navalplanner/web/orders/OrderModel.java
@@ -50,6 +50,7 @@ import org.navalplanner.business.externalcompanies.daos.IExternalCompanyDAO;
 import org.navalplanner.business.externalcompanies.entities.ExternalCompany;
 import org.navalplanner.business.labels.daos.ILabelDAO;
 import org.navalplanner.business.labels.entities.Label;
+import org.navalplanner.business.orders.daos.IHoursGroupDAO;
 import org.navalplanner.business.orders.daos.IOrderDAO;
 import org.navalplanner.business.orders.daos.IOrderElementDAO;
 import org.navalplanner.business.orders.entities.HoursGroup;
@@ -173,6 +174,9 @@ public class OrderModel implements IOrderModel {
     @Autowired
     private IOrderVersionDAO orderVersionDAO;
 
+    @Autowired
+    private IHoursGroupDAO hoursGroupDAO;
+
     @Override
     @Transactional(readOnly = true)
     public List<Label> getLabels() {
@@ -507,6 +511,7 @@ public class OrderModel implements IOrderModel {
 
     private void saveOnTransaction(boolean newOrderVersionNeeded) {
         checkConstraintOrderUniqueCode();
+        checkConstraintHoursGroupUniqueCode();
 
         reattachCriterions();
         reattachTasksForTasksSources();
@@ -538,6 +543,26 @@ public class OrderModel implements IOrderModel {
         calculateAdvancePercentageIncludingChildren(order);
     }
 
+    private void checkConstraintHoursGroupUniqueCode() {
+        HoursGroup repeatedHoursGroup;
+
+        repeatedHoursGroup = order.findRepeatedHoursGroupCode();
+        if (repeatedHoursGroup != null) {
+            throw new ValidationException(_(
+                    "Repeated Hours Group code {0} in Order {1}",
+                    repeatedHoursGroup.getCode(), repeatedHoursGroup
+                            .getParentOrderLine().getName()));
+        }
+
+        repeatedHoursGroup = hoursGroupDAO.findRepeatedHoursGroupCodeInDB(order.getHoursGroups());
+        if (repeatedHoursGroup != null) {
+            throw new ValidationException(_(
+                    "Repeated Hours Group code {0} in Order {1}",
+                    repeatedHoursGroup.getCode(), repeatedHoursGroup
+                            .getParentOrderLine().getName()));
+        }
+    }
+
     private void checkConstraintOrderUniqueCode() {
         OrderElement repeatedOrder;