diff --git a/libc/SYSCALLS.TXT b/libc/SYSCALLS.TXT
index f81b89f..ac8db62 100644
--- a/libc/SYSCALLS.TXT
+++ b/libc/SYSCALLS.TXT
@@ -77,7 +77,6 @@
 int     setgroups:setgroups32(int, const gid_t*)   arm,x86
 int     setgroups:setgroups(int, const gid_t*)     arm64,mips,mips64,x86_64
 int     setpgid(pid_t, pid_t)  all
-pid_t   vfork(void)  arm
 int     setregid:setregid32(gid_t, gid_t)  arm,x86
 int     setregid:setregid(gid_t, gid_t)    arm64,mips,mips64,x86_64
 int     chroot(const char*)  all
diff --git a/libc/arch-arm/arm.mk b/libc/arch-arm/arm.mk
index d72a160..b5283f6 100644
--- a/libc/arch-arm/arm.mk
+++ b/libc/arch-arm/arm.mk
@@ -42,6 +42,7 @@
     arch-arm/bionic/__restore.S \
     arch-arm/bionic/setjmp.S \
     arch-arm/bionic/syscall.S \
+    arch-arm/bionic/vfork.S \
 
 libc_arch_static_src_files_arm := arch-arm/bionic/exidx_static.c
 libc_arch_dynamic_src_files_arm := arch-arm/bionic/exidx_dynamic.c
diff --git a/libc/arch-arm/bionic/vfork.S b/libc/arch-arm/bionic/vfork.S
new file mode 100644
index 0000000..1b7cbad
--- /dev/null
+++ b/libc/arch-arm/bionic/vfork.S
@@ -0,0 +1,46 @@
+/*
+ * Copyright (C) 2015 The Android Open Source Project
+ * All rights reserved.
+ *
+ * Redistribution and use in source and binary forms, with or without
+ * modification, are permitted provided that the following conditions
+ * are met:
+ *  * Redistributions of source code must retain the above copyright
+ *    notice, this list of conditions and the following disclaimer.
+ *  * Redistributions in binary form must reproduce the above copyright
+ *    notice, this list of conditions and the following disclaimer in
+ *    the documentation and/or other materials provided with the
+ *    distribution.
+ *
+ * THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
+ * "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
+ * LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
+ * FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
+ * COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
+ * INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
+ * BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES; LOSS
+ * OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER CAUSED
+ * AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT LIABILITY,
+ * OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY OUT
+ * OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
+ * SUCH DAMAGE.
+ */
+
+#include <private/bionic_asm.h>
+
+ENTRY(vfork)
+    // __get_tls()[TLS_SLOT_THREAD_ID]->cached_pid_ = 0
+    mrc     p15, 0, r3, c13, c0, 3
+    ldr     r3, [r3, #4]
+    mov     r0, #0
+    str     r0, [r3, #12]
+
+    mov     ip, r7
+    ldr     r7, =__NR_vfork
+    swi     #0
+    mov     r7, ip
+    cmn     r0, #(MAX_ERRNO + 1)
+    bxls    lr
+    neg     r0, r0
+    b       __set_errno_internal
+END(vfork)
diff --git a/libc/arch-arm/syscalls/vfork.S b/libc/arch-arm/syscalls/vfork.S
deleted file mode 100644
index 5f4cb3d..0000000
--- a/libc/arch-arm/syscalls/vfork.S
+++ /dev/null
@@ -1,14 +0,0 @@
-/* Generated by gensyscalls.py. Do not edit. */
-
-#include <private/bionic_asm.h>
-
-ENTRY(vfork)
-    mov     ip, r7
-    ldr     r7, =__NR_vfork
-    swi     #0
-    mov     r7, ip
-    cmn     r0, #(MAX_ERRNO + 1)
-    bxls    lr
-    neg     r0, r0
-    b       __set_errno_internal
-END(vfork)
diff --git a/libc/arch-arm64/bionic/vfork.S b/libc/arch-arm64/bionic/vfork.S
index b6a672d..92fa333 100644
--- a/libc/arch-arm64/bionic/vfork.S
+++ b/libc/arch-arm64/bionic/vfork.S
@@ -31,6 +31,11 @@
 #include <linux/sched.h>
 
 ENTRY(vfork)
+    // __get_tls()[TLS_SLOT_THREAD_ID]->cached_pid_ = 0
+    mrs     x0, tpidr_el0
+    ldr     x0, [x0, #8]
+    str     wzr, [x0, #20]
+
     mov     x0, #(CLONE_VM | CLONE_VFORK | SIGCHLD)
     mov     x1, xzr
     mov     x2, xzr
diff --git a/libc/arch-x86/bionic/vfork.S b/libc/arch-x86/bionic/vfork.S
index ca7af0f..5c71b8d 100644
--- a/libc/arch-x86/bionic/vfork.S
+++ b/libc/arch-x86/bionic/vfork.S
@@ -34,6 +34,12 @@
   popl    %ecx  // Grab the return address.
   .cfi_adjust_cfa_offset 4
   .cfi_rel_offset ecx, 0
+
+  // __get_tls()[TLS_SLOT_THREAD_ID]->cached_pid_ = 0
+  movl    %gs:0, %eax
+  movl    4(%eax), %eax
+  movl    $0, 12(%eax)
+
   movl    $__NR_vfork, %eax
   int     $0x80
   cmpl    $-MAX_ERRNO, %eax
diff --git a/libc/arch-x86_64/bionic/vfork.S b/libc/arch-x86_64/bionic/vfork.S
index 129f1db..3b32c66 100644
--- a/libc/arch-x86_64/bionic/vfork.S
+++ b/libc/arch-x86_64/bionic/vfork.S
@@ -32,6 +32,12 @@
 
 ENTRY(vfork)
   popq    %rdi  // Grab the return address.
+
+  // __get_tls()[TLS_SLOT_THREAD_ID]->cached_pid_ = 0
+  mov    %fs:0, %rax
+  mov    8(%rax), %rax
+  movl   $0, 20(%rax)
+
   movl    $__NR_vfork, %eax
   syscall
   pushq   %rdi  // Restore the return address.