diff --git a/src/handlers/auth.js b/src/handlers/auth.js
index 34777ac..01fbee6 100644
--- a/src/handlers/auth.js
+++ b/src/handlers/auth.js
@@ -10,6 +10,7 @@ import AppRouterClient from '../routerClients/AppRouterClient';
 import PagesRouterClient from '../routerClients/PagesRouterClient';
 import {NextRequest} from 'next/server';
 import RouterClient from '../routerClients/RouterClient';
+import {config} from '../config/index';
 
 /**
  * @type {Record<string,(routerClient: RouterClient) => Promise<void>>}
@@ -35,13 +36,26 @@ const getRoute = (endpoint) => {
 /**
  * @param {object} [request]
  * @param {string} [endpoint]
+ * @param {{onError: (error: Error) => void}} [options]
  * @returns {(req, res) => any}
  */
-export default (request, endpoint) => {
+export default (request, endpoint, options) => {
+  if (!config.clientOptions.authDomain)
+    throw new Error("env variable 'KINDE_ISSUER_URL' is not set");
+
+  if (!config.clientOptions.clientId)
+    throw new Error("env variable 'KINDE_CLIENT_ID' is not set");
+
+  if (!config.clientOptions.clientSecret)
+    throw new Error("env variable 'KINDE_CLIENT_SECRET' is not set");
+
+  if (!config.clientOptions.redirectURL)
+    throw new Error("env variable 'KINDE_SITE_URL' is not set");
+
   // For backwards compatibility in app router
   if (typeof request == 'object' && typeof endpoint == 'string') {
     // @ts-ignore
-    return appRouterHandler(request, {params: {kindeAuth: endpoint}});
+    return appRouterHandler(request, {params: {kindeAuth: endpoint}}, options);
   }
   /**
    *
@@ -51,7 +65,7 @@ export default (request, endpoint) => {
   return async function handler(req, res) {
     return isAppRouter(req)
       ? // @ts-ignore
-        appRouterHandler(req, res)
+        appRouterHandler(req, res, options)
       : // @ts-ignore
         pagesRouterHandler(req, res, request);
   };
@@ -61,9 +75,10 @@ export default (request, endpoint) => {
  *
  * @param {NextRequest} req
  * @param {{params: {kindeAuth: string}}} res
+ * @param {{onError?: () => void}} options
  * @returns
  */
-const appRouterHandler = async (req, res) => {
+const appRouterHandler = async (req, res, options) => {
   const {params} = res;
   let endpoint = params.kindeAuth;
   endpoint = Array.isArray(endpoint) ? endpoint[0] : endpoint;
@@ -71,7 +86,7 @@ const appRouterHandler = async (req, res) => {
 
   return route
     ? // @ts-ignore
-      await route(new AppRouterClient(req, res))
+      await route(new AppRouterClient(req, res, options))
     : new Response('This page could not be found.', {status: 404});
 };
 
diff --git a/src/handlers/callback.js b/src/handlers/callback.js
index 19f7803..9838a89 100644
--- a/src/handlers/callback.js
+++ b/src/handlers/callback.js
@@ -16,12 +16,17 @@ export const callback = async (routerClient) => {
   const postLoginRedirectURL = postLoginRedirectURLFromMemory
     ? postLoginRedirectURLFromMemory
     : config.postLoginRedirectURL;
-
-  await routerClient.kindeClient.handleRedirectToApp(
-    routerClient.sessionManager,
-    routerClient.getUrl()
-  );
+  try {
+    await routerClient.kindeClient.handleRedirectToApp(
+      routerClient.sessionManager,
+      routerClient.getUrl()
+    );
+  } catch (error) {
+    return routerClient.json({error: error.message}, {status: 500});
+  }
 
   if (typeof postLoginRedirectURL === 'string')
     return routerClient.redirect(postLoginRedirectURL);
+
+  return routerClient.redirect(config.redirectURL);
 };
diff --git a/src/routerClients/AppRouterClient.js b/src/routerClients/AppRouterClient.js
index 26ca105..4ad3c35 100644
--- a/src/routerClients/AppRouterClient.js
+++ b/src/routerClients/AppRouterClient.js
@@ -11,8 +11,9 @@ export default class AppRouterClient extends RouterClient {
    *
    * @param {NextRequest} req
    * @param {*} res
+   * @param {{onError?: () => void}} options
    */
-  constructor(req, res) {
+  constructor(req, res, options) {
     super();
     this.kindeClient = createKindeServerClient(
       config.grantType,
@@ -22,6 +23,7 @@ export default class AppRouterClient extends RouterClient {
     this.sessionManager = appRouterSessionManager(cookies());
     this.req = req;
     this.searchParams = req.nextUrl.searchParams;
+    this.onErrorCallback = options?.onError;
   }
 
   /**
@@ -63,4 +65,10 @@ export default class AppRouterClient extends RouterClient {
   getSearchParam(key) {
     return this.req.nextUrl.searchParams.get(key);
   }
+
+  onError(error) {
+    if (this.onErrorCallback) {
+      this.onErrorCallback(error);
+    }
+  }
 }
diff --git a/src/routerClients/RouterClient.js b/src/routerClients/RouterClient.js
index 513d70a..2b18943 100644
--- a/src/routerClients/RouterClient.js
+++ b/src/routerClients/RouterClient.js
@@ -13,12 +13,12 @@ export default class RouterClient {
   req;
   /** @type {URLSearchParams} */
   searchParams;
- 
+
   constructor() {
     if (this.constructor == RouterClient) {
       throw new Error("Abstract classes can't be instantiated.");
     }
-   }
+  }
 
   /**
    *
@@ -59,4 +59,8 @@ export default class RouterClient {
   getSearchParam(key) {
     throw new Error("Method 'getSearchParam()' must be implemented.");
   }
+
+  onError() {
+    throw new Error("Method 'onError()' must be implemented.");
+  }
 }