diff --git a/libc/arch-x86_64/syscalls/ftruncate.S b/libc/arch-x86_64/syscalls/ftruncate.S
index 11161a7..0b14403 100644
--- a/libc/arch-x86_64/syscalls/ftruncate.S
+++ b/libc/arch-x86_64/syscalls/ftruncate.S
@@ -2,6 +2,8 @@
 
 #include <private/bionic_asm.h>
 
+    .hidden __set_errno
+
 ENTRY(ftruncate)
     movl    $__NR_ftruncate, %eax
     syscall