diff --git a/libc/arch-arm/syscalls/ftruncate.S b/libc/arch-arm/syscalls/ftruncate.S
index 4a3d56c..168d722 100644
--- a/libc/arch-arm/syscalls/ftruncate.S
+++ b/libc/arch-arm/syscalls/ftruncate.S
@@ -2,6 +2,8 @@
 
 #include <private/bionic_asm.h>
 
+    .hidden __set_errno
+
 ENTRY(ftruncate)
     mov     ip, r7
     ldr     r7, =__NR_ftruncate