diff --git a/src/ini.c b/src/ini.c
index 503b17ae3..f5dfdef46 100644
--- a/src/ini.c
+++ b/src/ini.c
@@ -33,6 +33,7 @@
 #include <stdlib.h>
 #include <string.h>
 #include <wchar.h>
+#include <wctype.h>
 #define HAVE_STDARG_H
 #include <86box/86box.h>
 #include <86box/ini.h>