diff --git a/libc/arch-x86/syscalls/dup.S b/libc/arch-x86/syscalls/dup.S
index 5854471..98070e2 100644
--- a/libc/arch-x86/syscalls/dup.S
+++ b/libc/arch-x86/syscalls/dup.S
@@ -4,6 +4,8 @@
 
 ENTRY(dup)
     pushl   %ebx
+    .cfi_def_cfa_offset 4
+    .cfi_rel_offset ebx, 0
     mov     8(%esp), %ebx
     movl    $__NR_dup, %eax
     int     $0x80