diff --git a/roles/nameserver/templates/unbound_network.conf.j2 b/roles/nameserver/templates/unbound_network.conf.j2
index bb0a035..bc54174 100644
--- a/roles/nameserver/templates/unbound_network.conf.j2
+++ b/roles/nameserver/templates/unbound_network.conf.j2
@@ -9,7 +9,9 @@ server:
         interface: 127.0.0.53
         interface: ::1
         outgoing-interface: {{ ansible_default_ipv4.address }}
+        {% if ansible_default_ipv6 is defined %}
         outgoing-interface: {{ ansible_default_ipv6.address }}
+        {% endif %}
         access-control: 192.168.1.0/24 allow
         access-control: 192.168.3.0/24 allow
         access-control: 172.16.0.0/24 allow