diff --git a/libc/arch-x86/bionic/vfork.S b/libc/arch-x86/bionic/vfork.S
index 79d7899..24ede3d 100644
--- a/libc/arch-x86/bionic/vfork.S
+++ b/libc/arch-x86/bionic/vfork.S
@@ -27,6 +27,7 @@
  */
 
 #include <private/bionic_asm.h>
+#include <private/bionic_asm_tls.h>
 
 // This custom code preserves the return address across the system call.
 
@@ -38,7 +39,7 @@
 
   // __get_tls()[TLS_SLOT_THREAD_ID]->cached_pid_ = 0
   movl    %gs:0, %eax
-  movl    4(%eax), %eax
+  movl    (TLS_SLOT_THREAD_ID * 4)(%eax), %eax
   movl    $0, 12(%eax)
 
   movl    $__NR_vfork, %eax