diff --git a/org.adempiere.ui.zk/WEB-INF/src/org/adempiere/webui/component/NumberBox.java b/org.adempiere.ui.zk/WEB-INF/src/org/adempiere/webui/component/NumberBox.java
index d3f57e0549..0162d0dd82 100644
--- a/org.adempiere.ui.zk/WEB-INF/src/org/adempiere/webui/component/NumberBox.java
+++ b/org.adempiere.ui.zk/WEB-INF/src/org/adempiere/webui/component/NumberBox.java
@@ -355,6 +355,7 @@ public class NumberBox extends Div
         vbox.appendChild(row4);
 
         popup.appendChild(vbox);
+        popup.setWidgetListener("onOpen", "calc.clearAll('" + txtCalcId + "')");
         return popup;
     }