diff --git a/tests/sys/acl/Makefile b/tests/sys/acl/Makefile
index abc505efe90b..0f2bc98b787b 100644
--- a/tests/sys/acl/Makefile
+++ b/tests/sys/acl/Makefile
@@ -1,39 +1,41 @@
 # $FreeBSD$
 
 PACKAGE=	tests
 
 TESTSDIR=	${TESTSBASE}/sys/acl
 
 BINDIR=		${TESTSDIR}
 
 ${PACKAGE}FILES+=	tools-crossfs.test
 ${PACKAGE}FILES+=	tools-nfs4.test
 ${PACKAGE}FILES+=	tools-nfs4-psarc.test
 ${PACKAGE}FILES+=	tools-nfs4-trivial.test
 ${PACKAGE}FILES+=	tools-posix.test
 
 SCRIPTS+=	run
 
 ATF_TESTS_C+=	acl-api-test
 
 TAP_TESTS_SH+=	00
 TAP_TESTS_SH+=	01
 TAP_TESTS_SH+=	02
 TAP_TESTS_SH+=	03
 TAP_TESTS_SH+=	04
 
 .for t in ${TAP_TESTS_SH}
-TEST_METADATA.$t+=	required_user="root"
+# Tests hard-code a ZFS pool name of "acltools" and so cannot run in parallel.
+TEST_METADATA.$t+=	required_user="root" \
+			is_exclusive=true
 .endfor
 
 _ACL_PROGS=		getfacl setfacl
 
 .for t in 01 03 04
 TEST_METADATA.$t+=	required_programs="perl zpool ${_ACL_PROGS}"
 .endfor
 
 .for t in 00 02
 TEST_METADATA.$t+=	required_programs="perl ${_ACL_PROGS}"
 .endfor
 
 .include <bsd.test.mk>