diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index 182323b1acc5..145749460bec 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -1586,12 +1586,21 @@ backup_tests()
 	chk_prio_nr 0 1 1 0
 
 	# single address, backup
+	reset
+	ip netns exec $ns1 ./pm_nl_ctl limits 0 1
+	ip netns exec $ns1 ./pm_nl_ctl add 10.0.2.1 flags signal,backup
+	ip netns exec $ns2 ./pm_nl_ctl limits 1 1
+	run_tests $ns1 $ns2 10.0.1.1 0 0 0 slow nobackup
+	chk_join_nr "single address, backup" 1 1 1
+	chk_add_nr 1 1
+	chk_prio_nr 1 0 0 1
+
 	reset
 	ip netns exec $ns1 ./pm_nl_ctl limits 0 1
 	ip netns exec $ns1 ./pm_nl_ctl add 10.0.2.1 flags signal
 	ip netns exec $ns2 ./pm_nl_ctl limits 1 1
 	run_tests $ns1 $ns2 10.0.1.1 0 0 0 slow backup
-	chk_join_nr "single address, backup" 1 1 1
+	chk_join_nr "single address, switch to backup" 1 1 1
 	chk_add_nr 1 1
 	chk_prio_nr 1 0 0 0
 }