c++11 osx header problem

"/Applications/CMake 2.8-12.app/Contents/bin/cmake" -H/Users/username/c11Test -B/Users/username/build-c11Test-Desktop_Qt_5_2_1_clang_64bit-Default --check-build-system CMakeFiles/Makefile.cmake 0
"/Applications/CMake 2.8-12.app/Contents/bin/cmake" -E cmake_progress_start /Users/username/build-c11Test-Desktop_Qt_5_2_1_clang_64bit-Default/CMakeFiles /Users/username/build-c11Test-Desktop_Qt_5_2_1_clang_64bit-Default/CMakeFiles/progress.marks
/Applications/Xcode.app/Contents/Developer/usr/bin/make -f CMakeFiles/Makefile2 all
/Applications/Xcode.app/Contents/Developer/usr/bin/make -f CMakeFiles/c11Test.dir/build.make CMakeFiles/c11Test.dir/depend
cd /Users/username/build-c11Test-Desktop_Qt_5_2_1_clang_64bit-Default && "/Applications/CMake 2.8-12.app/Contents/bin/cmake" -E cmake_depends "Unix Makefiles" /Users/username/c11Test /Users/username/c11Test /Users/username/build-c11Test-Desktop_Qt_5_2_1_clang_64bit-Default /Users/username/build-c11Test-Desktop_Qt_5_2_1_clang_64bit-Default /Users/username/build-c11Test-Desktop_Qt_5_2_1_clang_64bit-Default/CMakeFiles/c11Test.dir/DependInfo.cmake --color=
Scanning dependencies of target c11Test
/Applications/Xcode.app/Contents/Developer/usr/bin/make -f CMakeFiles/c11Test.dir/build.make CMakeFiles/c11Test.dir/build
"/Applications/CMake 2.8-12.app/Contents/bin/cmake" -E cmake_progress_report /Users/username/build-c11Test-Desktop_Qt_5_2_1_clang_64bit-Default/CMakeFiles 1
[100%] Building CXX object CMakeFiles/c11Test.dir/main.cpp.o
/usr/bin/c++    -stdlib=libc++ -std=gnu++11   -o CMakeFiles/c11Test.dir/main.cpp.o -c /Users/username/c11Test/main.cpp
/Users/username/c11Test/main.cpp:11:20: error: no member named 'accumulate' in namespace 'std'
    int sum = std::accumulate(v.begin(), v.end(), 0);
              ~~~~~^
1 error generated.
make[2]: *** [CMakeFiles/c11Test.dir/main.cpp.o] Error 1
make[1]: *** [CMakeFiles/c11Test.dir/all] Error 2
make: *** [all] Error 2