diff --git a/include/nana/gui/widgets/tabbar.hpp b/include/nana/gui/widgets/tabbar.hpp
index 0e2e2e9c..a9cc70cb 100644
--- a/include/nana/gui/widgets/tabbar.hpp
+++ b/include/nana/gui/widgets/tabbar.hpp
@@ -1,7 +1,7 @@
 /**
  *	A Tabbar implementation
  *	Nana C++ Library(http://www.nanapro.org)
- *	Copyright(C) 2003-2016 Jinhao(cnjinhao@hotmail.com)
+ *	Copyright(C) 2003-2018 Jinhao(cnjinhao@hotmail.com)
  *
  *	Distributed under the Boost Software License, Version 1.0.
  *	(See accompanying file LICENSE_1_0.txt or copy at
@@ -42,9 +42,8 @@ namespace nana
 			: arg_tabbar<T>({wdg, v})
 		{}
 
-		bool remove = true;					///< determines whether to remove the item
-		bool close_attach_window = true;	///< determines whether to close the attached window. It is ignored if remove is false
-
+		mutable bool remove = true;					///< determines whether to remove the item
+		mutable bool close_attach_window = true;	///< determines whether to close the attached window. It is ignored if remove is false
 	};
 
 	namespace drawerbase