diff --git a/index.js b/index.js
index b1fb00a..154f267 100644
--- a/index.js
+++ b/index.js
@@ -2,20 +2,27 @@
 
 const fp = require('fastify-plugin')
 const verifyBearerAuthFactory = require('./lib/verify-bearer-auth-factory')
+const { FST_BEARER_AUTH_INVALID_LOG_LEVEL } = require('./lib/errors')
 
 function fastifyBearerAuth (fastify, options, done) {
-  const defaultLogLevel = 'error'
-  options = Object.assign({ addHook: true, verifyErrorLogLevel: defaultLogLevel }, options)
+  options = Object.assign({ addHook: true, verifyErrorLogLevel: 'error' }, options)
 
-  if (!Object.prototype.hasOwnProperty.call(fastify.log, 'error') ||
-    (typeof fastify.log.error) !== 'function') options.verifyErrorLogLevel = null
-  if (options.verifyErrorLogLevel != null &&
-    (typeof options.verifyErrorLogLevel !== 'string' ||
-      !Object.prototype.hasOwnProperty.call(fastify.log, options.verifyErrorLogLevel) ||
-      (typeof fastify.log[options.verifyErrorLogLevel]) !== 'function'
-    )) {
-    const invalidLogLevelError = Error(`fastify.log does not have level '${options.verifyErrorLogLevel}'`)
-    done(invalidLogLevelError)
+  if (
+    Object.prototype.hasOwnProperty.call(fastify.log, 'error') === false ||
+    typeof fastify.log.error !== 'function'
+  ) {
+    options.verifyErrorLogLevel = null
+  }
+
+  if (
+    options.verifyErrorLogLevel != null &&
+    (
+      typeof options.verifyErrorLogLevel !== 'string' ||
+      Object.prototype.hasOwnProperty.call(fastify.log, options.verifyErrorLogLevel) === false ||
+      typeof fastify.log[options.verifyErrorLogLevel] !== 'function'
+    )
+  ) {
+    done(new FST_BEARER_AUTH_INVALID_LOG_LEVEL(options.verifyErrorLogLevel))
   }
 
   if (options.addHook === true) {
diff --git a/lib/errors.js b/lib/errors.js
new file mode 100644
index 0000000..898b7e4
--- /dev/null
+++ b/lib/errors.js
@@ -0,0 +1,9 @@
+'use strict'
+
+const createError = require('@fastify/error')
+
+const FST_BEARER_AUTH_INVALID_LOG_LEVEL = createError('FST_BEARER_AUTH_INVALID_LOG_LEVEL', 'fastify.log does not have level \'%s\'')
+
+module.exports = {
+  FST_BEARER_AUTH_INVALID_LOG_LEVEL
+}
diff --git a/package.json b/package.json
index 285ef61..7a49191 100644
--- a/package.json
+++ b/package.json
@@ -39,6 +39,7 @@
     "tsd": "^0.30.0"
   },
   "dependencies": {
+    "@fastify/error": "^3.4.1",
     "fastify-plugin": "^4.0.0"
   },
   "pre-commit": [