diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/workorders/entities/TaskWork.java b/navalplanner-business/src/main/java/org/navalplanner/business/workorders/entities/TaskWork.java
index caf8326e8..5587022ae 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/workorders/entities/TaskWork.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/workorders/entities/TaskWork.java
@@ -20,17 +20,7 @@ public abstract class TaskWork {
 
     private Set<ActivityWork> activityWorks = new HashSet<ActivityWork>();
 
-    public Integer getWorkHours() {
-        int result = 0;
-        Set<ActivityWork> a = activityWorks;
-        for (ActivityWork activityWork : a) {
-            Integer workingHours = activityWork.getWorkingHours();
-            if (workingHours != null) {
-                result += workingHours;
-            }
-        }
-        return result;
-    }
+    public abstract Integer getWorkHours();
 
     public void setActivities(List<ActivityWork> activities) {
         this.activityWorks = new HashSet<ActivityWork>(activities);
diff --git a/navalplanner-business/src/main/java/org/navalplanner/business/workorders/entities/TaskWorkLeaf.java b/navalplanner-business/src/main/java/org/navalplanner/business/workorders/entities/TaskWorkLeaf.java
index bb748e282..e8777b633 100644
--- a/navalplanner-business/src/main/java/org/navalplanner/business/workorders/entities/TaskWorkLeaf.java
+++ b/navalplanner-business/src/main/java/org/navalplanner/business/workorders/entities/TaskWorkLeaf.java
@@ -5,6 +5,19 @@ import java.util.List;
 
 public class TaskWorkLeaf extends TaskWork {
 
+    @Override
+    public Integer getWorkHours() {
+        int result = 0;
+        List<ActivityWork> a = getActivities();
+        for (ActivityWork activityWork : a) {
+            Integer workingHours = activityWork.getWorkingHours();
+            if (workingHours != null) {
+                result += workingHours;
+            }
+        }
+        return result;
+    }
+
     @Override
     public List<TaskWork> getChildren() {
         return new ArrayList<TaskWork>();