diff --git a/combo_plugin_gnm/templatetags/gnm.py b/combo_plugin_gnm/templatetags/gnm.py
index 3d84ed9..c8ce485 100644
--- a/combo_plugin_gnm/templatetags/gnm.py
+++ b/combo_plugin_gnm/templatetags/gnm.py
@@ -838,3 +838,8 @@ def airquality_hack(cell, request):
         cell.id = None
         cell.save()
     return cell
+
+
+@register.simple_tag
+def get_known_tile_types():
+    return list(settings.JSON_CELL_TYPES.keys())