diff --git a/.eslintrc b/.eslintrc
index 2751224..f3f6d13 100644
--- a/.eslintrc
+++ b/.eslintrc
@@ -21,6 +21,9 @@
     "space-before-blocks": [2, "always"]
   },
   "env": {
-    "node": true
-  }
+    "node": true,
+    "mocha": true,
+    "es6": true
+  },
+  "extends": "eslint:recommended"
 }
diff --git a/src/integrations/express.js b/src/integrations/express.js
index e611f22..affa5c4 100644
--- a/src/integrations/express.js
+++ b/src/integrations/express.js
@@ -20,10 +20,10 @@ module.exports.expressJwtSecret = function (options) {
   }
 
   const client = new JwksClient(options);
-  const onError = options.handleSigningKeyError || handleSigningKeyError;
+  const onError = options.handleSigningKeyError || handleSigningKeyError;
 
   return function secretProvider(req, header, payload, cb) {
-    if (!header || !supportedAlg.includes(header.alg)) {
+    if (!header || !supportedAlg.includes(header.alg)) {
       return cb(null, null);
     }
 
diff --git a/src/integrations/hapi.js b/src/integrations/hapi.js
index 51ca8ff..cf53972 100644
--- a/src/integrations/hapi.js
+++ b/src/integrations/hapi.js
@@ -37,7 +37,7 @@ module.exports.hapiJwt2Key = function (options) {
   }
 
   const client = new JwksClient(options);
-  const onError = options.handleSigningKeyError || handleSigningKeyError;
+  const onError = options.handleSigningKeyError || handleSigningKeyError;
 
   return function secretProvider(decoded, cb) {
     // We cannot find a signing certificate if there is no header (no kid).
diff --git a/src/integrations/passport.js b/src/integrations/passport.js
index 6fed323..a3981e1 100644
--- a/src/integrations/passport.js
+++ b/src/integrations/passport.js
@@ -25,13 +25,15 @@ module.exports.passportJwtSecret = function (options) {
   }
 
   const client = new JwksClient(options);
-  const onError = options.handleSigningKeyError || handleSigningKeyError;
+  const onError = options.handleSigningKeyError || handleSigningKeyError;
 
   return function secretProvider(req, rawJwtToken, cb) {
     let decoded;
     try {
       decoded = JWT.decode(rawJwtToken, { complete: true });
-    } catch (err) {}
+    } catch (err) {
+      decoded = null;
+    }
 
     if (!decoded || !supportedAlg.includes(decoded.header.alg)) {
       return cb(null, null);
diff --git a/src/utils.js b/src/utils.js
index a8ff44a..6b06404 100644
--- a/src/utils.js
+++ b/src/utils.js
@@ -1,5 +1,4 @@
 const jose = require('jose');
-const JwksError = require('./errors/JwksError');
 
 function retrieveSigningKeys(keys) {
   const keystore = jose.JWKS.asKeyStore({ keys }, { ignoreErrors: true });
diff --git a/src/wrappers/cache.js b/src/wrappers/cache.js
index 6bd0307..5a1ace9 100644
--- a/src/wrappers/cache.js
+++ b/src/wrappers/cache.js
@@ -1,7 +1,7 @@
 const debug = require('debug');
 const memoizer = require('lru-memoizer');
 
-function cacheWrapper(client, { cacheMaxEntries = 5, cacheMaxAge = 600000 } = options) {
+function cacheWrapper(client, { cacheMaxEntries = 5, cacheMaxAge = 600000 }) {
   const logger = debug('jwks');
   logger(`Configured caching of signing keys. Max: ${cacheMaxEntries} / Age: ${cacheMaxAge}`);
   return memoizer.sync({
diff --git a/src/wrappers/interceptor.js b/src/wrappers/interceptor.js
index 601c58e..5f0eb1d 100644
--- a/src/wrappers/interceptor.js
+++ b/src/wrappers/interceptor.js
@@ -4,7 +4,7 @@ const retrieveSigningKeys = require('../utils').retrieveSigningKeys;
  * Uses getKeysInterceptor to allow users to retrieve keys from a file,
  * external cache, or provided object before falling back to the jwksUri endpoint
  */
-function getKeysInterceptor(client, { getKeysInterceptor } = options) {
+function getKeysInterceptor(client, { getKeysInterceptor }) {
   const getSigningKey = client.getSigningKey.bind(client);
 
   return async (kid) => {
diff --git a/src/wrappers/rateLimit.js b/src/wrappers/rateLimit.js
index 1dd2ef4..ebdf4cc 100644
--- a/src/wrappers/rateLimit.js
+++ b/src/wrappers/rateLimit.js
@@ -3,7 +3,7 @@ const { RateLimiter } = require('limiter');
 
 const JwksRateLimitError = require('../errors/JwksRateLimitError');
 
-function rateLimtWrapper(client, { jwksRequestsPerMinute = 10 } = options) {
+function rateLimtWrapper(client, { jwksRequestsPerMinute = 10 }) {
   const logger = debug('jwks');
   const getSigningKey = client.getSigningKey.bind(client);