diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index 00053852ca15..de350a6a46f5 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -1789,6 +1789,8 @@ chk_prio_nr()
 {
 	local mp_prio_nr_tx=$1
 	local mp_prio_nr_rx=$2
+	local mpj_syn=$3
+	local mpj_syn_ack=$4
 	local count
 
 	print_check "ptx"
@@ -1810,6 +1812,26 @@ chk_prio_nr()
 	else
 		print_ok
 	fi
+
+	print_check "syn backup"
+	count=$(mptcp_lib_get_counter ${ns1} "MPTcpExtMPJoinSynBackupRx")
+	if [ -z "$count" ]; then
+		print_skip
+	elif [ "$count" != "$mpj_syn" ]; then
+		fail_test "got $count JOIN[s] syn with Backup expected $mpj_syn"
+	else
+		print_ok
+	fi
+
+	print_check "synack backup"
+	count=$(mptcp_lib_get_counter ${ns2} "MPTcpExtMPJoinSynAckBackupRx")
+	if [ -z "$count" ]; then
+		print_skip
+	elif [ "$count" != "$mpj_syn_ack" ]; then
+		fail_test "got $count JOIN[s] synack with Backup expected $mpj_syn_ack"
+	else
+		print_ok
+	fi
 }
 
 chk_subflow_nr()
@@ -2767,7 +2789,7 @@ backup_tests()
 		sflags=nobackup speed=slow \
 			run_tests $ns1 $ns2 10.0.1.1
 		chk_join_nr 1 1 1
-		chk_prio_nr 0 1
+		chk_prio_nr 0 1 1 0
 	fi
 
 	# single address, backup
@@ -2780,7 +2802,7 @@ backup_tests()
 			run_tests $ns1 $ns2 10.0.1.1
 		chk_join_nr 1 1 1
 		chk_add_nr 1 1
-		chk_prio_nr 1 1
+		chk_prio_nr 1 1 0 0
 	fi
 
 	# single address with port, backup
@@ -2793,7 +2815,7 @@ backup_tests()
 			run_tests $ns1 $ns2 10.0.1.1
 		chk_join_nr 1 1 1
 		chk_add_nr 1 1
-		chk_prio_nr 1 1
+		chk_prio_nr 1 1 0 0
 	fi
 
 	if reset "mpc backup" &&
@@ -2802,7 +2824,7 @@ backup_tests()
 		speed=slow \
 			run_tests $ns1 $ns2 10.0.1.1
 		chk_join_nr 0 0 0
-		chk_prio_nr 0 1
+		chk_prio_nr 0 1 0 0
 	fi
 
 	if reset "mpc backup both sides" &&
@@ -2812,7 +2834,7 @@ backup_tests()
 		speed=slow \
 			run_tests $ns1 $ns2 10.0.1.1
 		chk_join_nr 0 0 0
-		chk_prio_nr 1 1
+		chk_prio_nr 1 1 0 0
 	fi
 
 	if reset "mpc switch to backup" &&
@@ -2821,7 +2843,7 @@ backup_tests()
 		sflags=backup speed=slow \
 			run_tests $ns1 $ns2 10.0.1.1
 		chk_join_nr 0 0 0
-		chk_prio_nr 0 1
+		chk_prio_nr 0 1 0 0
 	fi
 
 	if reset "mpc switch to backup both sides" &&
@@ -2831,7 +2853,7 @@ backup_tests()
 		sflags=backup speed=slow \
 			run_tests $ns1 $ns2 10.0.1.1
 		chk_join_nr 0 0 0
-		chk_prio_nr 1 1
+		chk_prio_nr 1 1 0 0
 	fi
 }
 
@@ -3231,7 +3253,7 @@ fullmesh_tests()
 		addr_nr_ns2=1 sflags=backup,fullmesh speed=slow \
 			run_tests $ns1 $ns2 10.0.1.1
 		chk_join_nr 2 2 2
-		chk_prio_nr 0 1
+		chk_prio_nr 0 1 1 0
 		chk_rm_nr 0 1
 	fi
 
@@ -3244,7 +3266,7 @@ fullmesh_tests()
 		sflags=nobackup,nofullmesh speed=slow \
 			run_tests $ns1 $ns2 10.0.1.1
 		chk_join_nr 2 2 2
-		chk_prio_nr 0 1
+		chk_prio_nr 0 1 1 0
 		chk_rm_nr 0 1
 	fi
 }
@@ -3425,7 +3447,7 @@ userspace_tests()
 		sflags=backup speed=slow \
 			run_tests $ns1 $ns2 10.0.1.1
 		chk_join_nr 1 1 0
-		chk_prio_nr 0 0
+		chk_prio_nr 0 0 0 0
 	fi
 
 	# userspace pm type prevents rm_addr