diff --git a/include/cxxopts.hpp b/include/cxxopts.hpp
index ee02c57..b411bcc 100644
--- a/include/cxxopts.hpp
+++ b/include/cxxopts.hpp
@@ -33,6 +33,7 @@ THE SOFTWARE.
 #include <exception>
 #include <limits>
 #include <list>
+#include <locale>
 #include <map>
 #include <memory>
 #include <sstream>