diff --git a/src/setting_defines.h b/src/setting_defines.h
--- a/src/setting_defines.h
+++ b/src/setting_defines.h
@@ -30,6 +30,7 @@ const char SettingGroup_Commands[] = "Co
 // mainwindow setting keys
 const char SG_MainWindow_Size[] = "size";
 const char SG_MainWindow_Pos[] = "pos";
+const char SG_MainWindow_ActivePanel[] = "activePanel";
 
 // port setting keys
 const char SG_Port_SelectedPort[] = "selectedPort";