diff --git a/src/envelopePlugin.ts b/src/envelopePlugin.ts
index fcc3c06..4ef3fb8 100644
--- a/src/envelopePlugin.ts
+++ b/src/envelopePlugin.ts
@@ -16,7 +16,7 @@ const resolveUserFn = async (context: any) => {
     return { id: 'user1' };
 }
 
-const validateUser = params => {
+const validateUser = (params: any) => {
     if (!params.user) {
         return new Error(`Unauthenticated!`)
     }