error: 'stoi' is not a member of 'std'

Пытаюсь собрать Nana библиотеку с помощью 32-битного MinGW+CMake+Clion и получаю ошибки:

[  1%] Building CXX object CMakeFiles/nana.dir/source/any.cpp.obj
[  2%] Building CXX object CMakeFiles/nana.dir/source/basic_types.cpp.obj
[  3%] Building CXX object CMakeFiles/nana.dir/source/charset.cpp.obj
[  5%] Building CXX object CMakeFiles/nana.dir/source/datetime.cpp.obj
[  6%] Building CXX object CMakeFiles/nana.dir/source/deploy.cpp.obj
[  7%] Building CXX object CMakeFiles/nana.dir/source/internationalization.cpp.obj
C:\code\c++\nana\source\basic_types.cpp: In constructor 'nana::color::color(std::__cxx11::string)':
C:\code\c++\nana\source\basic_types.cpp:131:13: error: 'stoi' is not a member of 'std'
    auto n = std::stoi(css_color.substr(pos + 1, endpos - pos - 1), nullptr, 16);
             ^
C:\code\c++\nana\source\basic_types.cpp:307:15: error: 'stod' is not a member of 'std'
     auto pr = std::stod(rgb[0].substr(0, rgb[0].size() - 1));
               ^
C:\code\c++\nana\source\basic_types.cpp:310:10: error: 'stod' is not a member of 'std'
     pr = std::stod(rgb[1].substr(0, rgb[1].size() - 1));
          ^
C:\code\c++\nana\source\basic_types.cpp:313:10: error: 'stod' is not a member of 'std'
     pr = std::stod(rgb[2].substr(0, rgb[2].size() - 1));
          ^
C:\code\c++\nana\source\basic_types.cpp:318:10: error: 'stod' is not a member of 'std'
     r_ = std::stod(rgb[0]);
          ^
C:\code\c++\nana\source\basic_types.cpp:321:10: error: 'stod' is not a member of 'std'
     g_ = std::stod(rgb[1]);
          ^
C:\code\c++\nana\source\basic_types.cpp:324:10: error: 'stod' is not a member of 'std'
     b_ = std::stod(rgb[2]);
          ^
C:\code\c++\nana\source\basic_types.cpp:333:13: error: 'stod' is not a member of 'std'
    auto h = std::stod(str);
             ^
C:\code\c++\nana\source\basic_types.cpp:343:13: error: 'stod' is not a member of 'std'
    auto s = std::stod(str.substr(0, str.size() - 1));
             ^
C:\code\c++\nana\source\basic_types.cpp:353:13: error: 'stod' is not a member of 'std'
    auto l = std::stod(str.substr(0, str.size() - 1));
             ^
C:\code\c++\nana\source\basic_types.cpp:366:9: error: 'stod' is not a member of 'std'
    a_ = std::stod(str);
         ^

Флаги стоят:

CMAKE_CXX_FLAGS         =  -std=c++14 -Wall -g
CMAKE_EXE_LINKER_FLAGS  = -libgcc -lstdc++

Версия компилятора тоже подходит. Не совсем могу понять причину ошибки: вроде бы все подходит, но ошибки есть.