diff --git a/libc/include/sys/auxv.h b/libc/include/sys/auxv.h
index 0d753c3..4611fcc 100644
--- a/libc/include/sys/auxv.h
+++ b/libc/include/sys/auxv.h
@@ -33,7 +33,7 @@
 
 __BEGIN_DECLS
 
-unsigned long int getauxval(unsigned long int type);
+unsigned long int getauxval(unsigned long int type) __INTRODUCED_IN(21);
 
 __END_DECLS