diff --git a/libc/SYSCALLS.TXT b/libc/SYSCALLS.TXT
index 7d4fdd7..8c5572e 100644
--- a/libc/SYSCALLS.TXT
+++ b/libc/SYSCALLS.TXT
@@ -88,7 +88,6 @@
 int     setregid:setregid(gid_t, gid_t)    lp64
 int     chroot(const char*)  all
 int     prctl(int, unsigned long, unsigned long, unsigned long, unsigned long) all
-long    __arch_prctl: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
@@ -366,6 +365,7 @@
 
 # x86-specific
 int     __set_thread_area:set_thread_area(void*) x86
+long arch_prctl(int, unsigned long) x86_64
 
 # vdso stuff.
 int __clock_getres:clock_getres(clockid_t, struct timespec*) all
diff --git a/libc/arch-x86_64/bionic/__set_tls.c b/libc/arch-x86_64/bionic/__set_tls.c
index 10fd36f..9460a03 100644
--- a/libc/arch-x86_64/bionic/__set_tls.c
+++ b/libc/arch-x86_64/bionic/__set_tls.c
@@ -27,11 +27,12 @@
  */
 
 #include <sys/cdefs.h>
-#include <asm/prctl.h>
-#include <stdint.h>
 
-extern int __arch_prctl(int, unsigned long);
+// ARCH_SET_FS is not exposed via <sys/prctl.h> or <linux/prctl.h>.
+#include <asm/prctl.h>
+
+extern int arch_prctl(int, unsigned long);
 
 __LIBC_HIDDEN__ int __set_tls(void* ptr) {
-  return __arch_prctl(ARCH_SET_FS, (uintptr_t) ptr);
+  return arch_prctl(ARCH_SET_FS, (unsigned long) ptr);
 }