--- a/arch/x86/um/Makefile
+++ b/arch/x86/um/Makefile
@@ -21,7 +21,7 @@
 obj-$(CONFIG_ELF_CORE) += elfcore.o
 
 subarch-y = ../lib/string_32.o ../lib/atomic64_32.o ../lib/atomic64_cx8_32.o
-subarch-y += ../kernel/sys_ia32.o
+subarch-y += ../kernel/sys_ia32.o ../lib/atomic64_386_32.o ../lib/cmpxchg8b_emu.o
 
 else