diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/util/MutableTreeModel.java b/ganttzk/src/main/java/org/zkoss/ganttz/util/MutableTreeModel.java
index 8b14f1b58..1883f5137 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/util/MutableTreeModel.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/util/MutableTreeModel.java
@@ -31,6 +31,8 @@ import java.util.ListIterator;
 import java.util.Map;
 import java.util.WeakHashMap;
 
+import org.apache.commons.logging.Log;
+import org.apache.commons.logging.LogFactory;
 import org.zkoss.zul.AbstractTreeModel;
 import org.zkoss.zul.event.TreeDataEvent;
 
@@ -39,6 +41,8 @@ import org.zkoss.zul.event.TreeDataEvent;
  */
 public class MutableTreeModel<T> extends AbstractTreeModel {
 
+    private static final Log LOG = LogFactory.getLog(MutableTreeModel.class);
+
     public interface IChildrenExtractor<T> {
 
         public List<? extends T> getChildren(T parent);
@@ -354,10 +358,14 @@ public class MutableTreeModel<T> extends AbstractTreeModel {
 
     public List<T> getParents(T node) {
         ArrayList<T> result = new ArrayList<T>();
-        T current = node;
-        while (!isRoot(current)) {
-            current = getParent(current);
-            result.add(current);
+        try {
+            T current = node;
+            while (!isRoot(current)) {
+                current = getParent(current);
+                result.add(current);
+            }
+        } catch (Exception e) {
+            LOG.error("Trying to get the parent of a removed node", e);
         }
         return result;
     }
diff --git a/libreplan-webapp/src/main/java/org/libreplan/web/tree/TreeController.java b/libreplan-webapp/src/main/java/org/libreplan/web/tree/TreeController.java
index 7f0a1e87f..7acb66f32 100644
--- a/libreplan-webapp/src/main/java/org/libreplan/web/tree/TreeController.java
+++ b/libreplan-webapp/src/main/java/org/libreplan/web/tree/TreeController.java
@@ -342,7 +342,11 @@ public abstract class TreeController<T extends ITreeNode<T>> extends
 
     public void remove(T element) {
         List<T> parentNodes = getModel().getParents(element);
-        getModel().removeNode(element);
+        try {
+            getModel().removeNode(element);
+        } catch (NullPointerException e) {
+            LOG.error("Trying to delete an already removed node", e);
+        }
         getRenderer().refreshHoursValueForNodes(parentNodes);
         getRenderer().refreshBudgetValueForNodes(parentNodes);
     }