diff --git a/tripleo_ansible/roles/tripleo-hieradata/templates/all_nodes.j2 b/tripleo_ansible/roles/tripleo-hieradata/templates/all_nodes.j2
index c3ff006a7..ed6caf90e 100644
--- a/tripleo_ansible/roles/tripleo-hieradata/templates/all_nodes.j2
+++ b/tripleo_ansible/roles/tripleo-hieradata/templates/all_nodes.j2
@@ -17,7 +17,7 @@
 {# <service>_short_bootstrap_node_name: hostname #}
 {%   set services = (groups[service] | default ([]) | list ) %}
 {%   if all_nodes_extra_map_data[service ~ '_short_bootstrap_node_name'] is defined %}
-{%     set services = services + all_nodes_extra_map_data[service ~ '_short_bootstrap_node_name'] %}
+{%     set services = services + [all_nodes_extra_map_data[service ~ '_short_bootstrap_node_name']] %}
 {%   endif %}
 {%   if (services | length) > 0 %}
 {%     set _ = all_nodes.__setitem__((service ~ '_short_bootstrap_node_name'), (services | sort | first)) %}