Index: head/lib/libc/x86/sys/Makefile.inc
===================================================================
--- head/lib/libc/x86/sys/Makefile.inc	(revision 312421)
+++ head/lib/libc/x86/sys/Makefile.inc	(revision 312422)
@@ -1,10 +1,10 @@
 # $FreeBSD$
 
 .PATH:	${LIBC_SRCTOP}/x86/sys
 
 SRCS+= \
 	__vdso_gettc.c
 
-.if ${MK_HYPERV} != "no"
+.if ${MACHINE_CPUARCH} == "amd64" && ${MK_HYPERV} != "no"
 CFLAGS+=	-DWANT_HYPERV
 .endif