diff --git a/schema/lib/elements/he_ipv6.xsd b/schema/lib/elements/he_ipv6.xsd
index 69bbb0e..b7bb149 100644
--- a/schema/lib/elements/he_ipv6.xsd
+++ b/schema/lib/elements/he_ipv6.xsd
@@ -4,6 +4,7 @@
            attributeFormDefault="unqualified">
 
   <xs:include schemaLocation="../types/net.xsd"/>
+  <xs:include schemaLocation="../types/linux.xsd"/>
   <xs:include schemaLocation="../types/he_ipv6.xsd"/>
 
   <xs:complexType name="e_he_ipv6_cred">
@@ -27,6 +28,7 @@
                   <xs:extension base="t_net_addr_ip6">
                     <!-- VERY most likely "64" but we can't define a default with required. -->
                     <xs:attribute name="prefix" type="t_he_ipv6_prefix" use="required"/>
+                    <xs:attribute name="iface" type="t_linux_iface_name" use="required"/>
                   </xs:extension>
                 </xs:simpleContent>
               </xs:complexType>
diff --git a/schema/lib/types/linux.xsd b/schema/lib/types/linux.xsd
index 379e74e..edfd0b7 100644
--- a/schema/lib/types/linux.xsd
+++ b/schema/lib/types/linux.xsd
@@ -83,10 +83,17 @@
 
     <xs:simpleType name="t_linux_iface_name">
         <xs:restriction base="xs:token">
-            <!-- https://github.com/systemd/systemd/blob/master/src/udev/udev-builtin-net_id.c.
-                 I have no idea if this will work. TODO: simplify, validate in-code. -->
+            <!-- I have no idea if this will work. TODO: simplify, validate in-code. -->
+            <!--
+            "New" predictable iface naming.
+            https://github.com/systemd/systemd/blob/master/src/udev/udev-builtin-net_id.c.
+            -->
             <xs:pattern
                     value="((en|sl|wl|ww)(b[0-9]+|c[a-z0-9]|o[0-9]+(n.*(d.*)?)?|s[0-9]+(f.*)?([nd].*)?|x([A-Fa-f0-9]:){5}[A-Fa-f0-9]|(P.*)?p[0-9]+s[0-9]+(([fnd].*)|u.*)?))"/>
+            <!--
+            Legacy naming.
+            -->
+            <xs:pattern value="(eth|wl(an)?)[0-9]*"/>
             <xs:whiteSpace value="collapse"/>
         </xs:restriction>
     </xs:simpleType>