diff --git a/Shorewall-perl/Shorewall/Tc.pm b/Shorewall-perl/Shorewall/Tc.pm
index 6e6ec1e2b..b493bd883 100644
--- a/Shorewall-perl/Shorewall/Tc.pm
+++ b/Shorewall-perl/Shorewall/Tc.pm
@@ -414,7 +414,8 @@ sub setup_traffic_shaping() {
 	       "qt tc qdisc del dev $device ingress",
 	       "run_tc qdisc add dev $device root handle $devnum: htb default $defmark",
 	       "${dev}_mtu=\$(get_device_mtu $device)",
-	       "run_tc class add dev $device parent $devnum: classid $devnum:1 htb rate $devref->{out_bandwidth} mtu \$${dev}_mtu"
+	       "${dev}_mtu1=\$(get_device_mtu1 $device)",
+	       "run_tc class add dev $device parent $devnum: classid $devnum:1 htb rate $devref->{out_bandwidth} \$${dev}_mtu1"
 	       );
 
 	my $inband = rate_to_kbit $devref->{in_bandwidth};
@@ -464,7 +465,7 @@ sub setup_traffic_shaping() {
 	}
 
 	emitj( "[ \$${dev}_mtu -gt $quantum ] && quantum=\$${dev}_mtu || quantum=$quantum",
-	       "run_tc class add dev $device parent $devref->{number}:1 classid $classid htb rate $rate ceil $tcref->{ceiling} prio $tcref->{priority} mtu \$${dev}_mtu quantum \$quantum",
+	       "run_tc class add dev $device parent $devref->{number}:1 classid $classid htb rate $rate ceil $tcref->{ceiling} prio $tcref->{priority} \$${dev}_mtu1 quantum \$quantum",
 	       "run_tc qdisc add dev $device parent $classid handle ${prefix}${mark}: sfq perturb 10"
 	       );
 	#
diff --git a/Shorewall-perl/prog.functions b/Shorewall-perl/prog.functions
index 906cf27fc..36c71b063 100644
--- a/Shorewall-perl/prog.functions
+++ b/Shorewall-perl/prog.functions
@@ -150,3 +150,18 @@ restore_dynamic_rules() {
     fi
 }
 
+get_device_mtu1() # $1 = device
+{
+    local output="$(ip link ls dev $1 2> /dev/null)" # quotes required for /bin/ash
+    local mtu
+
+    if [ -n "$output" ]; then
+	mtu=$(find_mtu $output)
+    else
+	return
+    fi
+
+    if [ -n "$mtu" ]; then
+	[ $mtu = 1500 ] || echo mtu $(($mtu + 100))
+    fi
+}