diff --git a/libc/include/wchar.h b/libc/include/wchar.h
index 625097e..91d6f24 100644
--- a/libc/include/wchar.h
+++ b/libc/include/wchar.h
@@ -81,23 +81,23 @@
 extern size_t            mbrlen(const char *, size_t, mbstate_t *);
 extern size_t            mbrtowc(wchar_t *, const char *, size_t, mbstate_t *);
 extern size_t mbsrtowcs(wchar_t*, const char**, size_t, mbstate_t*);
-extern size_t mbsnrtowcs(wchar_t*, const char**, size_t, size_t, mbstate_t*);
+extern size_t mbsnrtowcs(wchar_t*, const char**, size_t, size_t, mbstate_t*) __INTRODUCED_IN(21);
 extern wint_t            putwc(wchar_t, FILE *);
 extern wint_t            putwchar(wchar_t);
 extern int               swprintf(wchar_t *, size_t, const wchar_t *, ...);
 extern int               swscanf(const wchar_t *, const wchar_t *, ...);
 extern wint_t            ungetwc(wint_t, FILE *);
 extern int vfwprintf(FILE*, const wchar_t*, va_list);
-extern int vfwscanf(FILE*, const wchar_t*, va_list);
+extern int vfwscanf(FILE*, const wchar_t*, va_list) __INTRODUCED_IN(21);
 extern int vswprintf(wchar_t*, size_t, const wchar_t*, va_list);
-extern int vswscanf(const wchar_t*, const wchar_t*, va_list);
+extern int vswscanf(const wchar_t*, const wchar_t*, va_list) __INTRODUCED_IN(21);
 extern int vwprintf(const wchar_t*, va_list);
-extern int vwscanf(const wchar_t*, va_list);
+extern int vwscanf(const wchar_t*, va_list) __INTRODUCED_IN(21);
 extern wchar_t* wcpcpy (wchar_t*, const wchar_t *);
 extern wchar_t* wcpncpy (wchar_t*, const wchar_t *, size_t);
 extern size_t            wcrtomb(char *, wchar_t, mbstate_t *);
 extern int               wcscasecmp(const wchar_t *, const wchar_t *);
-extern int               wcscasecmp_l(const wchar_t *, const wchar_t *, locale_t);
+extern int wcscasecmp_l(const wchar_t*, const wchar_t*, locale_t) __INTRODUCED_IN(23);
 extern wchar_t          *wcscat(wchar_t *, const wchar_t *);
 extern wchar_t          *wcschr(const wchar_t *, wchar_t);
 extern int               wcscmp(const wchar_t *, const wchar_t *);
@@ -107,24 +107,24 @@
 extern size_t            wcsftime(wchar_t *, size_t, const wchar_t *, const struct tm *) __LIBC_ABI_PUBLIC__;
 extern size_t            wcslen(const wchar_t *);
 extern int               wcsncasecmp(const wchar_t *, const wchar_t *, size_t);
-extern int               wcsncasecmp_l(const wchar_t *, const wchar_t *, size_t, locale_t);
+extern int wcsncasecmp_l(const wchar_t*, const wchar_t*, size_t, locale_t) __INTRODUCED_IN(23);
 extern wchar_t          *wcsncat(wchar_t *, const wchar_t *, size_t);
 extern int               wcsncmp(const wchar_t *, const wchar_t *, size_t);
 extern wchar_t          *wcsncpy(wchar_t *, const wchar_t *, size_t);
-extern size_t wcsnrtombs(char*, const wchar_t**, size_t, size_t, mbstate_t*);
+extern size_t wcsnrtombs(char*, const wchar_t**, size_t, size_t, mbstate_t*) __INTRODUCED_IN(21);
 extern wchar_t          *wcspbrk(const wchar_t *, const wchar_t *);
 extern wchar_t          *wcsrchr(const wchar_t *, wchar_t);
 extern size_t wcsrtombs(char*, const wchar_t**, size_t, mbstate_t*);
 extern size_t            wcsspn(const wchar_t *, const wchar_t *);
 extern wchar_t          *wcsstr(const wchar_t *, const wchar_t *);
 extern double wcstod(const wchar_t*, wchar_t**);
-extern float wcstof(const wchar_t*, wchar_t**);
+extern float wcstof(const wchar_t*, wchar_t**) __INTRODUCED_IN(21);
 extern wchar_t* wcstok(wchar_t*, const wchar_t*, wchar_t**);
 extern long wcstol(const wchar_t*, wchar_t**, int);
-extern long long wcstoll(const wchar_t*, wchar_t**, int);
-extern long double wcstold(const wchar_t*, wchar_t**);
+extern long long wcstoll(const wchar_t*, wchar_t**, int) __INTRODUCED_IN(21);
+extern long double wcstold(const wchar_t*, wchar_t**) __INTRODUCED_IN(21);
 extern unsigned long wcstoul(const wchar_t*, wchar_t**, int);
-extern unsigned long long wcstoull(const wchar_t*, wchar_t**, int);
+extern unsigned long long wcstoull(const wchar_t*, wchar_t**, int) __INTRODUCED_IN(21);
 extern int               wcswidth(const wchar_t *, size_t);
 extern size_t            wcsxfrm(wchar_t *, const wchar_t *, size_t);
 extern int               wctob(wint_t);
@@ -133,25 +133,25 @@
 extern int               wmemcmp(const wchar_t *, const wchar_t *, size_t);
 extern wchar_t          *wmemcpy(wchar_t *, const wchar_t *, size_t);
 #if defined(__USE_GNU)
-extern wchar_t          *wmempcpy(wchar_t *, const wchar_t *, size_t);
+extern wchar_t* wmempcpy(wchar_t*, const wchar_t*, size_t) __INTRODUCED_IN(23);
 #endif
 extern wchar_t          *wmemmove(wchar_t *, const wchar_t *, size_t);
 extern wchar_t          *wmemset(wchar_t *, wchar_t, size_t);
 extern int               wprintf(const wchar_t *, ...);
 extern int               wscanf(const wchar_t *, ...);
 
-extern long long          wcstoll_l(const wchar_t *, wchar_t **, int, locale_t);
-extern unsigned long long wcstoull_l(const wchar_t *, wchar_t **, int, locale_t);
-extern long double        wcstold_l(const wchar_t *, wchar_t **, locale_t );
+extern long long wcstoll_l(const wchar_t*, wchar_t**, int, locale_t) __INTRODUCED_IN(21);
+extern unsigned long long wcstoull_l(const wchar_t*, wchar_t**, int, locale_t) __INTRODUCED_IN(21);
+extern long double wcstold_l(const wchar_t*, wchar_t**, locale_t) __INTRODUCED_IN(21);
 
-extern int    wcscoll_l(const wchar_t *, const wchar_t *, locale_t);
-extern size_t wcsxfrm_l(wchar_t *, const wchar_t *, size_t, locale_t);
+extern int wcscoll_l(const wchar_t*, const wchar_t*, locale_t) __INTRODUCED_IN(21);
+extern size_t wcsxfrm_l(wchar_t*, const wchar_t*, size_t, locale_t) __INTRODUCED_IN(21);
 
 extern size_t wcslcat(wchar_t*, const wchar_t*, size_t);
 extern size_t wcslcpy(wchar_t*, const wchar_t*, size_t);
 
 #if __POSIX_VISIBLE >= 200809
-FILE* open_wmemstream(wchar_t**, size_t*);
+FILE* open_wmemstream(wchar_t**, size_t*) __INTRODUCED_IN(23);
 wchar_t* wcsdup(const wchar_t*);
 size_t wcsnlen(const wchar_t*, size_t);
 #endif