diff --git a/src/GroupGUI/GroupGUI_GroupDlg.cxx b/src/GroupGUI/GroupGUI_GroupDlg.cxx
index 8391cb3bf..07f5eae4e 100644
--- a/src/GroupGUI/GroupGUI_GroupDlg.cxx
+++ b/src/GroupGUI/GroupGUI_GroupDlg.cxx
@@ -473,7 +473,7 @@ void GroupGUI_GroupDlg::SelectionIntoArgument()
     }
   }
   else { // an attempt to synchronize list box selection with 3d viewer
-    if (myBusy) {
+    if ( myBusy || myMainObj->_is_nil() ) {
       return;
     }
 
@@ -617,7 +617,8 @@ int GroupGUI_GroupDlg::getSelectedSubshapes (TColStd_IndexedMapOfInteger& theMap
   theMapIndex.Clear();
 
   SalomeApp_Application* app = myGeomGUI->getApp();
-  if (!app) return 0;
+  if ( !app || myMainObj->_is_nil() )
+    return 0;
 
   LightApp_SelectionMgr* aSelMgr = app->selectionMgr();
   SALOME_ListIO aSelList;