diff --git a/libc/include/stdio_ext.h b/libc/include/stdio_ext.h
index de5d715..fdf6772 100644
--- a/libc/include/stdio_ext.h
+++ b/libc/include/stdio_ext.h
@@ -38,14 +38,14 @@
 
 __BEGIN_DECLS
 
-size_t __fbufsize(FILE*);
-int __freadable(FILE*);
-int __fwritable(FILE*);
-int __flbf(FILE*);
-void __fpurge(FILE*);
-size_t __fpending(FILE*);
-void _flushlbf(void);
-int __fsetlocking(FILE*, int);
+size_t __fbufsize(FILE*) __INTRODUCED_IN(23);
+int __freadable(FILE*) __INTRODUCED_IN(23);
+int __fwritable(FILE*) __INTRODUCED_IN(23);
+int __flbf(FILE*) __INTRODUCED_IN(23);
+void __fpurge(FILE*) __INTRODUCED_IN(23);
+size_t __fpending(FILE*) __INTRODUCED_IN(23);
+void _flushlbf(void) __INTRODUCED_IN(23);
+int __fsetlocking(FILE*, int) __INTRODUCED_IN(23);
 
 __END_DECLS