diff --git a/linux-2.6-xen-sparse/arch/x86_64/ia32/Makefile b/linux-2.6-xen-sparse/arch/x86_64/ia32/Makefile
index 0045b23f7e..6dcd7cf5ac 100644
--- a/linux-2.6-xen-sparse/arch/x86_64/ia32/Makefile
+++ b/linux-2.6-xen-sparse/arch/x86_64/ia32/Makefile
@@ -33,6 +33,8 @@ AFLAGS_vsyscall-syscall.o = -m32 -Iarch/i386/kernel
 
 ifdef CONFIG_XEN
 AFLAGS_vsyscall-int80.o = -m32 -Iarch/i386/kernel
+CFLAGS_syscall32-xen.o += -DUSE_INT80
+AFLAGS_syscall32_syscall-xen.o += -DUSE_INT80
 
 $(obj)/syscall32_syscall-xen.o: \
 	$(foreach F,int80 sysenter syscall,$(obj)/vsyscall-$F.so)