diff --git a/libc/include/sys/personality.h b/libc/include/sys/personality.h
index 7764468..68ae77c 100644
--- a/libc/include/sys/personality.h
+++ b/libc/include/sys/personality.h
@@ -34,7 +34,7 @@
 
 __BEGIN_DECLS
 
-extern int personality (unsigned int persona);
+extern int personality(unsigned int persona) __INTRODUCED_IN(21);
 
 __END_DECLS