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 0973393f0..a44473129 100644
--- a/ganttzk/src/main/java/org/zkoss/ganttz/util/LongOperationFeedback.java
+++ b/ganttzk/src/main/java/org/zkoss/ganttz/util/LongOperationFeedback.java
@@ -80,7 +80,7 @@ public class LongOperationFeedback {
                 } catch (Exception e) {
                     throw new RuntimeException(e);
                 } finally {
-                    alreadyInside.set(false);
+                    alreadyInside.remove();
                     Clients.showBusy(null, false);
                 }
             }