diff --git a/libc/SYSCALLS.TXT b/libc/SYSCALLS.TXT
index bb014bc..6465de4 100644
--- a/libc/SYSCALLS.TXT
+++ b/libc/SYSCALLS.TXT
@@ -94,6 +94,7 @@
 # IMPORTANT: Even though <sys/prctl.h> declares prctl(int, ...), the syscall stub must take 6 arguments
 #            to match the kernel implementation.
 int     prctl(int option, unsigned int arg2, unsigned int arg3, unsigned int arg4, unsigned int arg5) all
+long    arch_prctl(int, unsigned long) x86_64
 int     capget(cap_user_header_t header, cap_user_data_t data) all
 int     capset(cap_user_header_t header, const cap_user_data_t data) all
 int     sigaltstack(const stack_t*, stack_t*) all