diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/TaskGroup.java b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/TaskGroup.java
index 7a61b5c14..d8c3beed5 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/TaskGroup.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/planner/entities/TaskGroup.java
@@ -31,6 +31,7 @@ import java.util.Set;
 
 import org.apache.commons.lang.Validate;
 import org.hibernate.validator.AssertTrue;
+import org.hibernate.validator.Valid;
 import org.navalplanner.business.common.entities.ProgressType;
 import org.navalplanner.business.orders.entities.TaskSource;
 import org.navalplanner.business.resources.daos.IResourceDAO;
@@ -102,6 +103,7 @@ public class TaskGroup extends TaskElement {
     }
 
     @Override
+    @Valid
     public List<TaskElement> getChildren() {
         return Collections.unmodifiableList(taskElements);
     }