diff --git a/usr.sbin/makefs/tests/Makefile b/usr.sbin/makefs/tests/Makefile
index 842c4d566259..d7df64ab5a7f 100644
--- a/usr.sbin/makefs/tests/Makefile
+++ b/usr.sbin/makefs/tests/Makefile
@@ -3,9 +3,14 @@
 .include <src.opts.mk>
 
 ATF_TESTS_SH+=	makefs_cd9660_tests
+TEST_METADATA.makefs_cd9660_tests+=	required_files="/sbin/mount_cd9660"
 ATF_TESTS_SH+=	makefs_ffs_tests
 .if ${MK_ZFS} != "no"
 ATF_TESTS_SH+=	makefs_zfs_tests
+# ZFS pools created by makefs always have the same GUID, so OpenZFS
+# refuses to import more than one at a time.  Thus the ZFS tests cannot
+# be run in parallel for now.
+TEST_METADATA.makefs_zfs_tests+=	is_exclusive="true"
 .endif
 
 BINDIR=		${TESTSDIR}
@@ -14,8 +19,6 @@ BINDIR=		${TESTSDIR}
 SCRIPTS+=	makefs_tests_common.sh
 SCRIPTSNAME_makefs_tests_common.sh=	makefs_tests_common.sh
 
-TEST_METADATA.makefs_cd9660_tests+=	required_files="/sbin/mount_cd9660"
-
 .for t in ${ATF_TESTS_SH}
 TEST_METADATA.$t+=	required_user="root"
 .endfor