diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/Planner.java b/ganttzk/src/main/java/org/zkoss/ganttz/Planner.java
index 756f1bf15..ffed73efe 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/Planner.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/Planner.java
@@ -29,18 +29,18 @@ import java.util.HashMap;
 import java.util.HashSet;
 import java.util.List;
 import java.util.Map;
-import java.util.Set;
 import java.util.Map.Entry;
+import java.util.Set;
 
 import org.zkoss.ganttz.adapters.IDisabilityConfiguration;
 import org.zkoss.ganttz.adapters.IDomainAndBeansMapper;
 import org.zkoss.ganttz.adapters.PlannerConfiguration;
 import org.zkoss.ganttz.data.Dependency;
 import org.zkoss.ganttz.data.GanttDiagramGraph;
-import org.zkoss.ganttz.data.Position;
-import org.zkoss.ganttz.data.Task;
 import org.zkoss.ganttz.data.GanttDiagramGraph.GanttZKDiagramGraph;
 import org.zkoss.ganttz.data.GanttDiagramGraph.IGraphChangeListener;
+import org.zkoss.ganttz.data.Position;
+import org.zkoss.ganttz.data.Task;
 import org.zkoss.ganttz.extensions.ICommand;
 import org.zkoss.ganttz.extensions.ICommandOnTask;
 import org.zkoss.ganttz.extensions.IContext;
@@ -50,9 +50,9 @@ import org.zkoss.ganttz.timetracker.TimeTrackerComponentWithoutColumns;
 import org.zkoss.ganttz.timetracker.zoom.ZoomLevel;
 import org.zkoss.ganttz.util.ComponentsFinder;
 import org.zkoss.ganttz.util.LongOperationFeedback;
+import org.zkoss.ganttz.util.LongOperationFeedback.ILongOperation;
 import org.zkoss.ganttz.util.OnZKDesktopRegistry;
 import org.zkoss.ganttz.util.WeakReferencedListeners;
-import org.zkoss.ganttz.util.LongOperationFeedback.ILongOperation;
 import org.zkoss.ganttz.util.WeakReferencedListeners.IListenerNotification;
 import org.zkoss.ganttz.util.script.IScriptsRegister;
 import org.zkoss.zk.ui.Component;
@@ -553,6 +553,10 @@ public class Planner extends HtmlMacroComponent  {
     }
 
     public void setInitialZoomLevel(final ZoomLevel zoomLevel) {
+        if (this.initialZoomLevel != null) {
+            // already initialized
+            return;
+        }
         this.initialZoomLevel = zoomLevel;
     }