diff --git a/reactos/lib/kernel32/k32.h b/reactos/lib/kernel32/k32.h
index 1955cc43c9c..85e8c65340b 100755
--- a/reactos/lib/kernel32/k32.h
+++ b/reactos/lib/kernel32/k32.h
@@ -3,6 +3,7 @@
 #define NTOS_MODE_USER
 #define __NO_CTYPE_INLINES
 #include <ntos.h>
+#include <ctype.h>
 #include <stdarg.h>
 #include <stdio.h>
 #include <limits.h>