diff --git a/include/pocketpy/common/str.h b/include/pocketpy/common/str.h
index 34836cc8..f6842c91 100644
--- a/include/pocketpy/common/str.h
+++ b/include/pocketpy/common/str.h
@@ -13,10 +13,6 @@ typedef struct c11_string{
     int size;
 } c11_string;
 
-#ifndef isascii
-#define isascii(c) ((unsigned)(c) < 0x80)
-#endif
-
 typedef struct pkpy_Str{
     int size;
     bool is_ascii;