diff --git a/tests/sys/netpfil/pf/Makefile b/tests/sys/netpfil/pf/Makefile
index 7256602a55a9..250299727697 100644
--- a/tests/sys/netpfil/pf/Makefile
+++ b/tests/sys/netpfil/pf/Makefile
@@ -1,62 +1,65 @@
 # $FreeBSD$
 
 PACKAGE=	tests
 
 TESTSDIR=       ${TESTSBASE}/sys/netpfil/pf
 TESTS_SUBDIRS+=	ioctl
 
 ATF_TESTS_SH+=	altq \
 		anchor \
 		dup \
 		ether \
 		forward \
 		fragmentation \
 		get_state \
 		icmp \
 		killstate \
 		macro \
 		map_e \
 		match \
 		modulate \
 		names \
 		nat \
 		pass_block \
 		pfsync	\
 		prio \
 		proxy \
 		rdr \
 		ridentifier \
 		route_to \
 		rtable \
 		rules_counter \
 		scrub \
 		set_skip \
 		set_tos \
 		src_track \
 		syncookie \
 		synproxy \
 		table \
 		tos
 
+# Tests reuse jail names and so cannot run in parallel.
+TEST_METADATA+=	is_exclusive=true
+
 ${PACKAGE}FILES+=	CVE-2019-5597.py \
 			CVE-2019-5598.py \
 			daytime_inetd.conf \
 			echo_inetd.conf \
 			fragcommon.py \
 			frag-overindex.py \
 			frag-overlimit.py \
 			frag-overreplace.py \
 			pfsync_defer.py \
 			pft_ether.py \
 			utils.subr
 
 ${PACKAGE}FILESMODE_CVE-2019-5597.py=	0555
 ${PACKAGE}FILESMODE_CVE-2019-5598.py=	0555
 ${PACKAGE}FILESMODE_fragcommon.py=	0555
 ${PACKAGE}FILESMODE_frag-overindex.py=	0555
 ${PACKAGE}FILESMODE_frag-overlimit.py=	0555
 ${PACKAGE}FILESMODE_frag-overreplace.py=	0555
 ${PACKAGE}FILESMODE_pfsync_defer.py=	0555
 ${PACKAGE}FILESMODE_pft_ether.py=	0555
 
 .include <bsd.test.mk>