Index: lib/libthr/Makefile
===================================================================
--- lib/libthr/Makefile
+++ lib/libthr/Makefile
@@ -16,6 +16,11 @@
 SHLIB_MAJOR= 3
 NO_WTHREAD_SAFETY=1
 NO_WCAST_ALIGN.gcc=1    # for gcc 4.2
+
+.if ${MACHINE_ARCH} == "powerpc64"
+NO_WCAST_ALIGN.clang=1  # for clang 8
+.endif
+
 CFLAGS+=-DPTHREAD_KERNEL
 CFLAGS+=-I${SRCTOP}/lib/libc/include -I${.CURDIR}/thread \
 	-I${SRCTOP}/include