diff --git a/lib/types/request.d.ts b/lib/types/request.d.ts
index c987216db..078fc3c95 100644
--- a/lib/types/request.d.ts
+++ b/lib/types/request.d.ts
@@ -27,23 +27,24 @@ export interface AppCredentials {
  * User-extensible type for request.auth credentials.
  */
 export interface AuthCredentials<
-    AuthUser extends object = UserCredentials,
-    AuthApp extends object = AppCredentials,
+    AuthUser = UserCredentials,
+    AuthApp = AppCredentials
 > {
     /**
      * The application scopes to be granted.
      * [See docs](https://github.com/hapijs/hapi/blob/master/API.md#-routeoptionsauthaccessscope)
      */
     scope?: string[] | undefined;
+
     /**
      * If set, will only work with routes that set `access.entity` to `user`.
      */
-    user?: MergeType<UserCredentials, AuthUser> | undefined;
+    user?: AuthUser
 
     /**
      * If set, will only work with routes that set `access.entity` to `app`.
      */
-    app?: MergeType<AppCredentials, AuthApp> | undefined;
+    app?: AuthApp;
 }
 
 export interface AuthArtifacts {
@@ -65,15 +66,20 @@ export type AuthMode = 'required' | 'optional' | 'try';
  * [See docs](https://github.com/hapijs/hapi/blob/master/API.md#-requestauth)
  */
 export interface RequestAuth<
-    AuthUser extends object = UserCredentials,
-    AuthApp extends object = AppCredentials,
-    CredentialsExtra extends object = Record<string, unknown>,
+    AuthUser = UserCredentials,
+    AuthApp = AppCredentials,
+    CredentialsExtra = Record<string, unknown>,
     ArtifactsExtra = Record<string, unknown>
 > {
     /** an artifact object received from the authentication strategy and used in authentication-related actions. */
     artifacts: ArtifactsExtra;
     /** the credential object received during the authentication process. The presence of an object does not mean successful authentication. */
-    credentials: MergeType<CredentialsExtra, AuthCredentials<AuthUser, AuthApp>>;
+    credentials: (
+
+        AuthCredentials<AuthUser, AuthApp> &
+        CredentialsExtra
+    );
+
     /** the authentication error is failed and mode set to 'try'. */
     error: Error;
     /** true if the request has been successfully authenticated, otherwise false. */
@@ -89,6 +95,7 @@ export interface RequestAuth<
     strategy: string;
 }
 
+
 /**
  * 'peek' - emitted for each chunk of payload data read from the client connection. The event method signature is function(chunk, encoding).
  * 'finish' - emitted when the request payload finished reading. The event method signature is function ().
@@ -296,7 +303,12 @@ export type ReqRef = Partial<Record<keyof ReqRefDefaults, unknown>>;
 /**
  * Utilities for merging request refs and other things
  */
-export type MergeType<T extends object, U extends object> = Omit<T, keyof U> & U;
+export type MergeType<T, U> = {
+    [K in keyof T]: K extends keyof U
+        ? U[K]
+        : T[K];
+};
+
 export type MergeRefs<T extends ReqRef> = MergeType<ReqRefDefaults, T>;
 
 /**
diff --git a/lib/types/response.d.ts b/lib/types/response.d.ts
index 4b19ebc31..f7c131787 100644
--- a/lib/types/response.d.ts
+++ b/lib/types/response.d.ts
@@ -6,7 +6,6 @@ import {
     UserCredentials,
     AppCredentials,
     AuthArtifacts,
-    MergeType,
     AuthCredentials,
     ReqRef,
     ReqRefDefaults,
@@ -386,19 +385,19 @@ export type ResponseValue = string | object;
 
 export interface AuthenticationData<
 
-    AuthUser extends object = UserCredentials,
-    AuthApp extends object = AppCredentials,
-    CredentialsExtra extends object = Record<string, unknown>,
+    AuthUser = UserCredentials,
+    AuthApp = AppCredentials,
+    CredentialsExtra = Record<string, unknown>,
     ArtifactsExtra = AuthArtifacts
 > {
-    credentials: MergeType<CredentialsExtra, AuthCredentials<AuthUser, AuthApp>>;
+    credentials: AuthCredentials<AuthUser, AuthApp> & CredentialsExtra;
     artifacts?: ArtifactsExtra | undefined;
 }
 
 export interface Auth<
-    AuthUser extends object = UserCredentials,
-    AuthApp extends object = AppCredentials,
-    CredentialsExtra extends object = Record<string, unknown>,
+    AuthUser = UserCredentials,
+    AuthApp = AppCredentials,
+    CredentialsExtra = Record<string, unknown>,
     ArtifactsExtra = AuthArtifacts
 > {
     readonly isAuth: true;
@@ -459,9 +458,9 @@ export interface ResponseToolkit<Refs extends ReqRef = ReqRefDefaults> {
      * @return Return value: an internal authentication object.
      */
     authenticated <
-        AuthUser extends object = MergeRefs<Refs>['AuthUser'],
-        AuthApp  extends object = MergeRefs<Refs>['AuthApp'],
-        CredentialsExtra extends object = MergeRefs<Refs>['AuthCredentialsExtra'],
+        AuthUser = MergeRefs<Refs>['AuthUser'],
+        AuthApp  = MergeRefs<Refs>['AuthApp'],
+        CredentialsExtra = MergeRefs<Refs>['AuthCredentialsExtra'],
         ArtifactsExtra = MergeRefs<Refs>['AuthArtifactsExtra']
     >(
         data: (
@@ -537,9 +536,9 @@ export interface ResponseToolkit<Refs extends ReqRef = ReqRefDefaults> {
      * [See docs](https://github.com/hapijs/hapi/blob/master/API.md#-hunauthenticatederror-data)
      */
     unauthenticated <
-        AuthUser extends object = MergeRefs<Refs>['AuthUser'],
-        AuthApp extends object = MergeRefs<Refs>['AuthApp'],
-        CredentialsExtra extends object = MergeRefs<Refs>['AuthCredentialsExtra'],
+        AuthUser = MergeRefs<Refs>['AuthUser'],
+        AuthApp = MergeRefs<Refs>['AuthApp'],
+        CredentialsExtra = MergeRefs<Refs>['AuthCredentialsExtra'],
         ArtifactsExtra = MergeRefs<Refs>['AuthArtifactsExtra']
     >(
         error: Error,
diff --git a/test/types/index.ts b/test/types/index.ts
index 35fd0a49e..724d87283 100644
--- a/test/types/index.ts
+++ b/test/types/index.ts
@@ -10,6 +10,7 @@ import {
     Server,
     ServerRoute,
     server as createServer,
+    UserCredentials,
     ServerRegisterPluginObject,
     Lifecycle,
     CachedServerMethod
@@ -17,6 +18,20 @@ import {
 
 const { expect: check } = lab;
 
+type IsAny<T> = (
+    unknown extends T
+      ? [keyof T] extends [never] ? false : true
+      : false
+  );
+
+
+declare module '../..' {
+    interface UserCredentials {
+        someId: string;
+        someName: string;
+    }
+}
+
 interface ServerAppSpace {
     multi?: number;
 }
@@ -29,6 +44,21 @@ check.type<MyServer>(server);
 
 server.app.multi = 10;
 
+const genericRoute: ServerRoute = {
+    method: 'GET',
+    path: '/',
+    handler: (request, h) => {
+
+        check.type<UserCredentials>(request.auth.credentials!.user!);
+
+        const y: IsAny<typeof request.auth.credentials> = false;
+
+        return 'hello!';
+    }
+}
+
+server.route(genericRoute);
+
 interface RequestDecorations {
     Server: MyServer;
     RequestApp: {
@@ -36,6 +66,22 @@ interface RequestDecorations {
     },
     RouteApp: {
         prefix: string[];
+    },
+    AuthUser: {
+        id: string,
+        name: string
+        email: string
+    },
+    AuthCredentialsExtra: {
+        test: number
+    }
+    AuthApp: {
+        key: string
+        name: string
+    },
+    AuthArtifactsExtra: {
+        some: string
+        thing: number
     }
 }
 
@@ -63,6 +109,21 @@ const route: ServerRoute<RequestDecorations> = {
         check.type<number>(request.server.app.multi!);
         check.type<string[]>(request.route.settings.app!.prefix);
 
+        check.type<number>(request.auth.credentials!.test);
+
+        check.type<string>(request.auth.credentials!.user!.email);
+        check.type<string>(request.auth.credentials!.user!.id);
+        check.type<string>(request.auth.credentials!.user!.name);
+
+        check.type<string>(request.auth.credentials!.app!.name);
+        check.type<string>(request.auth.credentials!.app!.key);
+
+        check.type<string>(request.auth.artifacts.some);
+        check.type<number>(request.auth.artifacts.thing);
+
+        const y: IsAny<typeof request.auth.credentials> = false;
+        const z: IsAny<typeof request.auth.artifacts> = false;
+
         return 'hello!'
     }
 };
@@ -135,7 +196,6 @@ server.method('test.add', (a: number, b: number) => a + b, {
     generateKey: (a: number, b: number) => `${a}${b}`
 });
 
-
 server.methods.test.add.cache?.drop(1, 2);
 
 declare module '../..' {