diff --git a/scripts/kconfig/menu.c b/scripts/kconfig/menu.c
index d64108bc0cf938e0304f63d19dd621ce01a77257..24547fe0fe9ee455aea7b17e13c949abcb4d5aab 100644
--- a/scripts/kconfig/menu.c
+++ b/scripts/kconfig/menu.c
@@ -3,6 +3,7 @@
  * Released under the terms of the GNU GPL v2.0.
  */
 
+#include <ctype.h>
 #include <stdarg.h>
 #include <stdlib.h>
 #include <string.h>