diff --git a/children.json b/children.json
index b260c5729..43693a944 100644
--- a/children.json
+++ b/children.json
@@ -60,7 +60,7 @@
       "  {% set value = tags.amenity %}",
       "{% endif %}",
       "",
-      "{% set type_data = const[key + '=' + value] |default(const['default=yes']) %}"
+      "{% set type_data = const[key ~ '=' ~ value] |default(const['default=yes']) %}"
     ],
     "title": "{{ keyTrans(key) }}: {{localizedTag(tags, 'name') |default(localizedTag(tags, 'operator')) | default(localizedTag(tags, 'ref')) | default(tagTrans(key, value)) }}",
     "description": "{{ type_data }}",