diff --git a/libc/arch-x86/syscalls/sigaltstack.S b/libc/arch-x86/syscalls/sigaltstack.S
index 58a2997..71fdb12 100644
--- a/libc/arch-x86/syscalls/sigaltstack.S
+++ b/libc/arch-x86/syscalls/sigaltstack.S
@@ -5,6 +5,9 @@
 ENTRY(sigaltstack)
     pushl   %ebx
     pushl   %ecx
+    .cfi_def_cfa_offset 8
+    .cfi_rel_offset ebx, 0
+    .cfi_rel_offset ecx, 4
     mov     12(%esp), %ebx
     mov     16(%esp), %ecx
     movl    $__NR_sigaltstack, %eax