diff --git a/arch/um/sys-x86_64/Makefile b/arch/um/sys-x86_64/Makefile
index 2201e9c20e4..c1ea9eb0446 100644
--- a/arch/um/sys-x86_64/Makefile
+++ b/arch/um/sys-x86_64/Makefile
@@ -8,7 +8,8 @@ obj-y = bug.o bugs.o delay.o fault.o ldt.o mem.o ptrace.o ptrace_user.o \
 	setjmp.o signal.o stub.o stub_segv.o syscalls.o syscall_table.o \
 	sysrq.o ksyms.o tls.o
 
-subarch-obj-y = lib/csum-partial_64.o lib/memcpy_64.o lib/thunk_64.o
+subarch-obj-y = lib/csum-partial_64.o lib/memcpy_64.o lib/thunk_64.o \
+		lib/rwsem_64.o
 subarch-obj-$(CONFIG_MODULES) += kernel/module.o
 
 ldt-y = ../sys-i386/ldt.o