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 99e30ba25..abfa15d72 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
@@ -1,6 +1,7 @@
 package org.navalplanner.business.planner.entities;
 
 import java.util.ArrayList;
+import java.util.Collections;
 import java.util.List;
 
 import org.apache.commons.lang.Validate;
@@ -13,7 +14,7 @@ public class TaskGroup extends TaskElement {
     private List<TaskElement> taskElements = new ArrayList<TaskElement>();
 
     public List<TaskElement> getTaskElements() {
-        return taskElements;
+        return Collections.unmodifiableList(taskElements);
     }
 
     public void addTaskElement(TaskElement task) {
diff --git a/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/TaskGroupTest.java b/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/TaskGroupTest.java
index eed56ba63..acbc58b9b 100644
--- a/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/TaskGroupTest.java
+++ b/navalplanner-business/src/test/java/org/navalplanner/business/test/planner/TaskGroupTest.java
@@ -42,4 +42,9 @@ public class TaskGroupTest {
     public void cantAddNullTaskElement() {
         taskGroup.addTaskElement(null);
     }
+
+    @Test(expected = UnsupportedOperationException.class)
+    public void taskElementsCollectionCannotBeModified() {
+        taskGroup.getTaskElements().set(0, null);
+    }
 }