diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/IWorkerDAO.java b/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/IWorkerDAO.java
index d12d00ed9..7435403eb 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/IWorkerDAO.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/IWorkerDAO.java
@@ -118,4 +118,12 @@ public interface IWorkerDAO extends IIntegrationEntityDAO<Worker> {
     List<Object[]> getWorkingHoursGroupedPerWorker(List<String> workerNifs,
             Date startingDate, Date endingDate);
 
+    Worker findByNifAnotherTransaction(String nif)
+            throws InstanceNotFoundException;
+
+    public List<Worker> findByFirstNameSecondName(String firstname,
+            String secondname);
+
+    public List<Worker> findByFirstNameSecondNameAnotherTransaction(
+            String firstname, String secondname);
 }
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/WorkerDAO.java b/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/WorkerDAO.java
index 5de16d2f2..f561c31bb 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/WorkerDAO.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/resources/daos/WorkerDAO.java
@@ -53,10 +53,9 @@ public class WorkerDAO extends IntegrationEntityDAO<Worker>
     @Override
     public Worker findUniqueByNif(String nif) throws InstanceNotFoundException {
         Criteria criteria = getSession().createCriteria(Worker.class);
-        criteria.add(Restrictions.eq("nif", nif).ignoreCase());
+        criteria.add(Restrictions.eq("nif", nif.trim()).ignoreCase());
 
         List<Worker> list = criteria.list();
-
         if (list.size() != 1) {
             throw new InstanceNotFoundException(nif, Worker.class.getName());
         }
@@ -64,6 +63,13 @@ public class WorkerDAO extends IntegrationEntityDAO<Worker>
         return list.get(0);
     }
 
+    @Override
+    @Transactional(readOnly = true, propagation = Propagation.REQUIRES_NEW)
+    public Worker findByNifAnotherTransaction(String nif)
+            throws InstanceNotFoundException {
+        return findUniqueByNif(nif);
+    }
+
     @Override
     public List<Worker> getWorkers() {
         return getSession().createQuery(
@@ -122,6 +128,22 @@ public class WorkerDAO extends IntegrationEntityDAO<Worker>
         return findByFirstNameSecondNameAndNif(firstname, secondname, nif);
     }
 
+    @SuppressWarnings("unchecked")
+    @Override
+    public List<Worker> findByFirstNameSecondName(String firstname,
+            String secondname) {
+        return getSession().createCriteria(Worker.class).add(
+                Restrictions.and(Restrictions.ilike("firstName", firstname),
+                        Restrictions.ilike("surname", secondname))).list();
+    }
+
+    @Override
+    @Transactional(readOnly = true, propagation = Propagation.REQUIRES_NEW)
+    public List<Worker> findByFirstNameSecondNameAnotherTransaction(
+            String firstname, String secondname) {
+        return findByFirstNameSecondName(firstname, secondname);
+    }
+
     @Override
     @Transactional(readOnly = true)
     public List<HoursWorkedPerWorkerDTO> getWorkingHoursPerWorker(List<Worker> workers, Date startingDate, Date endingDate) {
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/VirtualWorker.java b/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/VirtualWorker.java
index 7b53a5a9d..32b8cd27f 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/VirtualWorker.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/VirtualWorker.java
@@ -75,7 +75,7 @@ public class VirtualWorker extends Worker {
 
     @AssertTrue
     @Override
-    public boolean checkConstraintUniqueFirstNameSurnameNif() {
+    public boolean checkConstraintUniqueNif() {
         return true;
     }
 
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/Worker.java b/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/Worker.java
index ddc5403ea..77d0d5e53 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/Worker.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/resources/entities/Worker.java
@@ -21,12 +21,11 @@
 package org.navalplanner.business.resources.entities;
 
 
-import java.util.List;
-
 import org.apache.commons.lang.StringUtils;
 import org.hibernate.validator.AssertTrue;
 import org.hibernate.validator.NotEmpty;
 import org.navalplanner.business.common.Registry;
+import org.navalplanner.business.common.exceptions.InstanceNotFoundException;
 
 /**
  * This class models a worker.
@@ -142,31 +141,27 @@ public class Worker extends Resource {
         return !isVirtual();
     }
 
-    @AssertTrue(message = "Worker with the same first name, surname and nif previously existed")
-    public boolean checkConstraintUniqueFirstNameSurnameNif() {
-
+    @AssertTrue(message = "Worker with the same nif previously existed")
+    public boolean checkConstraintUniqueNif() {
         if (!areFirstNameSurnameNifSpecified()) {
             return true;
         }
 
+        try {
         /* Check the constraint. */
-        List<Worker> list = Registry.getWorkerDAO()
-                .findByFirstNameSecondNameAndNifAnotherTransaction(firstName,
-                        surname, nif);
-
-        if (isNewObject()) {
-            return list.isEmpty();
-        } else {
-            if (list.isEmpty()) {
-                return true;
+            Worker worker = Registry.getWorkerDAO()
+                    .findByNifAnotherTransaction(nif);
+            if (isNewObject()) {
+                return false;
             } else {
-                return list.get(0).getId().equals(getId());
+                return worker.getId().equals(getId());
             }
+        } catch (InstanceNotFoundException e) {
+            return isNewObject();
         }
-
     }
 
-   private boolean areFirstNameSurnameNifSpecified() {
+    protected boolean areFirstNameSurnameNifSpecified() {
 
        return !StringUtils.isBlank(firstName) &&
            !StringUtils.isBlank(surname) &&
diff --git a/navalplanner-webapp/src/test/java/org/navalplanner/web/test/ws/resources/api/ResourceServiceTest.java b/navalplanner-webapp/src/test/java/org/navalplanner/web/test/ws/resources/api/ResourceServiceTest.java
index c1c95e002..6727ce4c7 100644
--- a/navalplanner-webapp/src/test/java/org/navalplanner/web/test/ws/resources/api/ResourceServiceTest.java
+++ b/navalplanner-webapp/src/test/java/org/navalplanner/web/test/ws/resources/api/ResourceServiceTest.java
@@ -395,7 +395,8 @@ public class ResourceServiceTest {
         machineDTO.criterionSatisfactions.add(
             new CriterionSatisfactionDTO(workerCt.getName() , "c1",
                 getDate(2001, 1, 1), null)); // Incorrect type.
-        WorkerDTO workerDTO = new WorkerDTO(getUniqueName(), "surname", "nif");
+        WorkerDTO workerDTO = new WorkerDTO(getUniqueName(), "surname",
+                getUniqueName());
         workerDTO.criterionSatisfactions.add(
             new CriterionSatisfactionDTO(machineCt.getName() , "c1",
                 getDate(2001, 1, 1), null)); // Incorrect type.
@@ -746,7 +747,8 @@ public class ResourceServiceTest {
         m1.resourcesCostCategoryAssignments.add(m1a1);
 
         /* Create a worker DTO. */
-        WorkerDTO w1 = new WorkerDTO(getUniqueName(), "surname", "nif");
+        String nif = getUniqueName();
+        WorkerDTO w1 = new WorkerDTO(getUniqueName(), "surname", nif);
         CriterionSatisfactionDTO w1s1 = new CriterionSatisfactionDTO(ct
                 .getName(), "c1", getDate(2000, 1, 1), getDate(2000, 2, 1));
         w1.criterionSatisfactions.add(w1s1);