diff --git a/configure.ac b/configure.ac
index 9f8c878..540cd73 100644
--- a/configure.ac
+++ b/configure.ac
@@ -2,9 +2,10 @@ AC_CONFIG_MACRO_DIR([m4])
 AC_INIT([shiranui],[1.0.0],[tomo832@gmail.com])
 AM_INIT_AUTOMAKE([subdir-objects foreign -Wall -Werror -Wno-portability])
 # for better message,use https://www.gnu.org/software/autoconf-archive/ax_cxx_compile_stdcxx_11.html#ax_cxx_compile_stdcxx_11
-CXXFLAGS="$CXXFLAGS -std=c++11 -O2"
+CXXFLAGS="$CXXFLAGS -O2"
 AC_LANG([C++])
 AC_PROG_CXX
+AX_CXX_COMPILE_STDCXX_11
 AX_BOOST_BASE
 AX_BOOST_PROGRAM_OPTIONS
 AX_BOOST_SYSTEM