diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/common/daos/IGenericDao.java b/navalplanner-business/src/main/java/org/navalplanner/business/common/daos/IGenericDao.java
index 913b69ebb..3bb29be8c 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/common/daos/IGenericDao.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/common/daos/IGenericDao.java
@@ -46,10 +46,10 @@ public interface IGenericDao <E, PK extends Serializable>{
      * <br/>
      * If the check is not passed,
      * <code>org.springframework.dao.OptimisticLockingFailureException</code>
-     * is thrown. If the key of the entity is <code>null</code> or the entity
-     * does not exist in database, the check is considered to be successful.
-     * This lets client code to treat creation and modification of instances in
-     * a unified way.
+     * is thrown. If the key or the version of the entity is <code>null</code>,
+     * or the entity does not exist in database, the check is considered to be
+     * successful. This lets client code to treat creation and modification of
+     * instances in a unified way.
      */
     public void checkVersion(E entity);
 
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/common/daos/impl/GenericDaoHibernate.java b/navalplanner-business/src/main/java/org/navalplanner/business/common/daos/impl/GenericDaoHibernate.java
index f227032d2..8afb7fc94 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/common/daos/impl/GenericDaoHibernate.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/common/daos/impl/GenericDaoHibernate.java
@@ -85,7 +85,7 @@ public class GenericDaoHibernate<E, PK extends Serializable> implements
 
         /* Get id and version from entity. */
         Serializable id;
-        long versionValueInMemory;
+        Long versionValueInMemory;
 
         try {
 
@@ -99,6 +99,10 @@ public class GenericDaoHibernate<E, PK extends Serializable> implements
             Method getVersionMethod = entityClass.getMethod("getVersion");
             versionValueInMemory = (Long) getVersionMethod.invoke(entity);
 
+            if (versionValueInMemory == null) {
+                return;
+            }
+
         } catch (Exception e) {
             throw new RuntimeException(e);
         }
@@ -116,7 +120,7 @@ public class GenericDaoHibernate<E, PK extends Serializable> implements
                 return;
             }
 
-            if (versionValueInMemory != versionValueInDB) {
+            if (!versionValueInMemory.equals(versionValueInDB)) {
                 throw new StaleObjectStateException(entityClass.getName(), id);
             }