diff --git a/luna/CType.h b/luna/CType.h
index 5e8fc45c..79daf531 100644
--- a/luna/CType.h
+++ b/luna/CType.h
@@ -75,4 +75,22 @@ inline constexpr int _toupper(int c)
 {
     if (_islower(c)) return c & 0x5f;
     return c;
-}
\ No newline at end of file
+}
+
+#if defined(_LUNA_OVERRIDE_STDC) || defined(IN_MOON)
+#define isalnum _isalnum
+#define isalpha _isalpha
+#define isascii _isascii
+#define iscntrl _iscntrl
+#define isdigit _isdigit
+#define isxdigit _isxdigit
+#define isspace _isspace
+#define ispunct _ispunct
+#define isprint _isprint
+#define isgraph _isgraph
+#define islower _islower
+#define isupper _isupper
+#define isblank _isblank
+#define tolower _tolower
+#define toupper _toupper
+#endif
\ No newline at end of file