diff --git a/CMakeLists.txt b/CMakeLists.txt
index bc75ce4..0cee64d 100644
--- a/CMakeLists.txt
+++ b/CMakeLists.txt
@@ -13,6 +13,13 @@ add_definitions(-D_GNU_SOURCE)
 set(CMAKE_C_STANDARD 99)
 set(CMAKE_CXX_STANDARD 11)
 
+# locale.h
+include(CheckIncludeFile)
+CHECK_INCLUDE_FILE("locale.h" HAVE_LOCALE_H)
+if(HAVE_LOCALE_H)
+    add_definitions(-DHAVE_LOCALE_H)
+endif()
+
 # GTK+
 find_package(PkgConfig REQUIRED)
 pkg_check_modules(GTK3 REQUIRED IMPORTED_TARGET "gtk+-3.0>=3.16.0")