diff --git a/lib/data_struct/dsl.rb b/lib/data_struct/dsl.rb
index af84adb..9549692 100644
--- a/lib/data_struct/dsl.rb
+++ b/lib/data_struct/dsl.rb
@@ -57,8 +57,8 @@ def define(name, field_definitions, &)
     # ActionController::Parameters#permit to permit all defined parameters.
     def param_keys(clazz = self)
       clazz.defined_attributes.map do |name, defn|
-        if explicit_permits[name]
-          { name => explicit_permits[name] }
+        if clazz.respond_to?(:explicit_permits) && clazz.explicit_permits[name]
+          { name => clazz.explicit_permits[name] }
         elsif defn.is_a?(Array)
           if defn[0].respond_to?(:defined_attributes)
             { name => param_keys(defn[0]) }