diff --git a/core/config/schema/core.data_types.schema.yml b/core/config/schema/core.data_types.schema.yml
index 1d0fc29..ca2506f 100644
--- a/core/config/schema/core.data_types.schema.yml
+++ b/core/config/schema/core.data_types.schema.yml
@@ -120,6 +120,10 @@ action_configuration_default:
   sequence:
     - type: string
 
+# Theme settings schema is automatically applied to a theme's *.settings
+# configuration unless the theme provides its own schema. Static analysis of
+# configuration objects using schema will have to duplicate the
+# system_config_schema_info_alter() to determine a theme's *.settings schema.
 theme_settings:
   type: mapping
   mapping: