diff --git a/src/widget/multilayerselecttree/multilayerselecttree.combo.js b/src/widget/multilayerselecttree/multilayerselecttree.combo.js
index fb6490468..fbfec9380 100644
--- a/src/widget/multilayerselecttree/multilayerselecttree.combo.js
+++ b/src/widget/multilayerselecttree/multilayerselecttree.combo.js
@@ -174,6 +174,11 @@ BI.MultiLayerSelectTreeCombo = BI.inherit(BI.Widget, {
                 action: function () {
                     self.trigger.stopEditing();
                 }
+            }, {
+                eventName: BI.Combo.EVENT_BEFORE_POPUPVIEW,
+                action: function () {
+                    self.fireEvent(BI.MultiLayerSelectTreeCombo.EVENT_BEFORE_POPUPVIEW);
+                }
             }]
         }
     },
diff --git a/src/widget/multilayersingletree/multilayersingletree.combo.js b/src/widget/multilayersingletree/multilayersingletree.combo.js
index 7446ff5f5..5534e27ac 100644
--- a/src/widget/multilayersingletree/multilayersingletree.combo.js
+++ b/src/widget/multilayersingletree/multilayersingletree.combo.js
@@ -176,6 +176,11 @@ BI.MultiLayerSingleTreeCombo = BI.inherit(BI.Widget, {
                 action: function () {
                     self.trigger.stopEditing();
                 }
+            }, {
+                eventName: BI.Combo.EVENT_BEFORE_POPUPVIEW,
+                action: function () {
+                    self.fireEvent(BI.MultiLayerSingleTreeCombo.EVENT_BEFORE_POPUPVIEW);
+                }
             }]
         }
     },