diff --git a/ganttzk/src/main/java/org/zkoss/ganttz/util/LongOperationFeedback.java b/ganttzk/src/main/java/org/zkoss/ganttz/util/LongOperationFeedback.java
index 4c6426607..ff35a0c8b 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/util/LongOperationFeedback.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/util/LongOperationFeedback.java
@@ -266,6 +266,9 @@ public class LongOperationFeedback {
                 if (current.isEnd()) {
                     return;
                 }
+                if (!desktop.isAlive()) {
+                    return;
+                }
                 try {
                     Executions.activate(desktop);
                 } catch (Exception e) {