diff --git a/libc/include/uchar.h b/libc/include/uchar.h
index 90af651..0c7424d 100644
--- a/libc/include/uchar.h
+++ b/libc/include/uchar.h
@@ -58,10 +58,8 @@
  *
  * Returns the number of bytes written to `__buf` on success, and returns -1 and sets `errno`
  * on failure.
- *
- * Available since API level 21.
  */
-size_t c16rtomb(char* _Nullable __buf, char16_t __ch16, mbstate_t* _Nullable __ps) __INTRODUCED_IN(21);
+size_t c16rtomb(char* _Nullable __buf, char16_t __ch16, mbstate_t* _Nullable __ps);
 
 /**
  * [c32rtomb(3)](http://man7.org/linux/man-pages/man3/c32rtomb.3.html) converts a single UTF-32
@@ -69,25 +67,19 @@
  *
  * Returns the number of bytes written to `__buf` on success, and returns -1 and sets `errno`
  * on failure.
- *
- * Available since API level 21.
  */
-size_t c32rtomb(char* _Nullable __buf, char32_t __ch32, mbstate_t* _Nullable __ps) __INTRODUCED_IN(21);
+size_t c32rtomb(char* _Nullable __buf, char32_t __ch32, mbstate_t* _Nullable __ps);
 
 /**
  * [mbrtoc16(3)](http://man7.org/linux/man-pages/man3/mbrtoc16.3.html) converts the next UTF-8
  * sequence to a UTF-16 code point.
- *
- * Available since API level 21.
  */
-size_t mbrtoc16(char16_t* _Nullable __ch16, const char* _Nullable __s, size_t __n, mbstate_t* _Nullable __ps) __INTRODUCED_IN(21);
+size_t mbrtoc16(char16_t* _Nullable __ch16, const char* _Nullable __s, size_t __n, mbstate_t* _Nullable __ps);
 
 /**
  * [mbrtoc32(3)](http://man7.org/linux/man-pages/man3/mbrtoc32.3.html) converts the next UTF-8
  * sequence to a UTF-32 code point.
- *
- * Available since API level 21.
  */
-size_t mbrtoc32(char32_t* _Nullable __ch32, const char* _Nullable __s, size_t __n, mbstate_t* _Nullable __ps) __INTRODUCED_IN(21);
+size_t mbrtoc32(char32_t* _Nullable __ch32, const char* _Nullable __s, size_t __n, mbstate_t* _Nullable __ps);
 
 __END_DECLS