diff --git a/libc/include/sys/wait.h b/libc/include/sys/wait.h
index 2317b02..aba20e5 100644
--- a/libc/include/sys/wait.h
+++ b/libc/include/sys/wait.h
@@ -51,7 +51,7 @@
 
 extern pid_t  wait(int *);
 extern pid_t  waitpid(pid_t, int *, int);
-extern pid_t  wait4(pid_t, int *, int, struct rusage *);
+extern pid_t wait4(pid_t, int*, int, struct rusage*) __INTRODUCED_IN(19);
 
 /* Posix states that idtype_t should be an enumeration type, but
  * the kernel headers define P_ALL, P_PID and P_PGID as constant macros