diff --git a/libc/arch-x86/syscalls/fdatasync.S b/libc/arch-x86/syscalls/fdatasync.S
index 9ddf03b..02e09be 100644
--- a/libc/arch-x86/syscalls/fdatasync.S
+++ b/libc/arch-x86/syscalls/fdatasync.S
@@ -4,6 +4,8 @@
 
 ENTRY(fdatasync)
     pushl   %ebx
+    .cfi_def_cfa_offset 4
+    .cfi_rel_offset ebx, 0
     mov     8(%esp), %ebx
     movl    $__NR_fdatasync, %eax
     int     $0x80