diff --git a/global/overlay/etc/puppet/modules/soc/templates/sso/docker-compose.yml.erb b/global/overlay/etc/puppet/modules/soc/templates/sso/docker-compose.yml.erb
index 184bdfa..c2e770c 100644
--- a/global/overlay/etc/puppet/modules/soc/templates/sso/docker-compose.yml.erb
+++ b/global/overlay/etc/puppet/modules/soc/templates/sso/docker-compose.yml.erb
@@ -25,7 +25,7 @@ services:
       - ./shibboleth/sp-key.pem:/etc/shibboleth/sp-key.pem
       - ./apache/401.html:/var/www/error/401.html:ro
 <% if @extra_proxy_conf -%>
-      - @extra_proxy_conf:@extra_proxy_conf
+      - <%= @extra_proxy_conf %>:<%= @extra_proxy_conf %>
 <% end -%>
 networks:
   sso: