diff --git a/src/interface.d.ts b/src/interface.d.ts
index 830972c..55c137b 100644
--- a/src/interface.d.ts
+++ b/src/interface.d.ts
@@ -63,6 +63,6 @@ type PieController = {
   model: (config: Object, session: Object, env: Object) => Promise<Object>;
   score: (config: Object, session: Object, env: Object) => Promise<Object>;
   createCorrectResponseSession: (config: Object, env: Object) => Promise<Object>;
-  validate: (model: Object, config: Object) => Object;
+  validate: (model: Object, config: Object) => any;
 };