diff --git a/roles/network-fastd/templates/fastd-backbone.j2 b/roles/network-fastd/templates/fastd-backbone.j2
index aa5b4c1..e396150 100644
--- a/roles/network-fastd/templates/fastd-backbone.j2
+++ b/roles/network-fastd/templates/fastd-backbone.j2
@@ -5,4 +5,5 @@
 #
 auto {{ item.0.id }}igvpn-{{ item.1.mtu }}
 iface {{ item.0.id }}igvpn-{{ item.1.mtu }}
+    mtu {{ item.1.mtu }}
     hwaddress {{ mac | hwaddr('linux') }}
diff --git a/roles/network-fastd/templates/fastd-mesh.j2 b/roles/network-fastd/templates/fastd-mesh.j2
index 0e484fc..e0e7fdc 100644
--- a/roles/network-fastd/templates/fastd-mesh.j2
+++ b/roles/network-fastd/templates/fastd-mesh.j2
@@ -5,4 +5,5 @@
 #
 auto {{ item.0.id }}vpn-{{ item.1.mtu }}
 iface {{ item.0.id }}vpn-{{ item.1.mtu }}
+    mtu {{ item.1.mtu }}
     hwaddress {{ mac | hwaddr('linux') }}