diff --git a/tools/testing/selftests/net/mptcp/mptcp_join.sh b/tools/testing/selftests/net/mptcp/mptcp_join.sh
index 231a95a8de9e..818a163c830c 100755
--- a/tools/testing/selftests/net/mptcp/mptcp_join.sh
+++ b/tools/testing/selftests/net/mptcp/mptcp_join.sh
@@ -1778,6 +1778,8 @@ 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"
@@ -1799,6 +1801,26 @@ 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()
@@ -2751,7 +2773,7 @@ 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
@@ -2764,7 +2786,7 @@ 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
@@ -2777,7 +2799,7 @@ 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" &&
@@ -2786,7 +2808,7 @@ 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" &&
@@ -2796,7 +2818,7 @@ 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" &&
@@ -2805,7 +2827,7 @@ 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" &&
@@ -2815,7 +2837,7 @@ 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
 }
 
@@ -3215,7 +3237,7 @@ 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
 
@@ -3228,7 +3250,7 @@ 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
 }
@@ -3407,7 +3429,7 @@ 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