diff --git a/hydra-gtk/src/main.c b/hydra-gtk/src/main.c
index 27fb84e..cccc1a0 100755
--- a/hydra-gtk/src/main.c
+++ b/hydra-gtk/src/main.c
@@ -10,6 +10,7 @@
 
 #include <gtk/gtk.h>
 #include <string.h>
+#include <locale.h>
 #include "interface.h"
 #include "support.h"
 #include "callbacks.h"