diff --git a/tools/testing/selftests/net/forwarding/mirror_lib.sh b/tools/testing/selftests/net/forwarding/mirror_lib.sh
index c33bfd7ba214290d8c7ab55ea2cbbbc215676d36..13db1cb50e57be6f229d4cdcccfc6cceabf3e6db 100644
--- a/tools/testing/selftests/net/forwarding/mirror_lib.sh
+++ b/tools/testing/selftests/net/forwarding/mirror_lib.sh
@@ -31,7 +31,7 @@ mirror_test()
 
 	local t0=$(tc_rule_stats_get $dev $pref)
 	$MZ $vrf_name ${sip:+-A $sip} -B $dip -a own -b bc -q \
-	    -c 10 -d 100ms -t icmp type=8
+	    -c 10 -d 100msec -t icmp type=8
 	sleep 0.5
 	local t1=$(tc_rule_stats_get $dev $pref)
 	local delta=$((t1 - t0))