diff --git a/.travis.yml b/.travis.yml
index 02ae7ab..86336cb 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -17,22 +17,33 @@ matrix:
     - php: 7.1
       env: PHPCS=1 DEFAULT=0
 
+    - php: 7.1
+      env: PHPSTAN=1 DEFAULT=0
+
+    - php: 5.6
+      env: PREFER_LOWEST=1
+
 before_script:
-  - if [[ $TRAVIS_PHP_VERSION != 7.0 ]]; then phpenv config-rm xdebug.ini; fi
+  - if [[ $TRAVIS_PHP_VERSION != 7.1 ]]; then phpenv config-rm xdebug.ini; fi
 
-  - composer install --prefer-dist --no-interaction
+  - if [[ $PREFER_LOWEST != 1 ]]; then composer update --no-interaction; fi
+  - if [[ $PREFER_LOWEST == 1 ]]; then composer update --no-interaction --prefer-lowest --prefer-stable; fi
 
   - if [[ $DEFAULT = 1 ]]; then mysql -e 'CREATE DATABASE cakephp_test;'; fi
 
   - if [[ $PHPCS = 1 ]]; then composer require cakephp/cakephp-codesniffer:^3.0; fi
+  - if [[ $PHPSTAN = 1 ]]; then composer require phpstan/phpstan; fi
 
 script:
-  - if [[ $DEFAULT = 1 && $TRAVIS_PHP_VERSION = 7.0 ]]; then vendor/bin/phpunit --coverage-clover=clover.xml; fi
-  - if [[ $DEFAULT = 1 && $TRAVIS_PHP_VERSION != 7.0 ]]; then vendor/bin/phpunit; fi
+  - if [[ $DEFAULT = 1 && $TRAVIS_PHP_VERSION = 7.1 ]]; then vendor/bin/phpunit --coverage-clover=clover.xml; fi
+  - if [[ $DEFAULT = 1 && $TRAVIS_PHP_VERSION != 7.1 ]]; then vendor/bin/phpunit; fi
+
   - if [[ $PHPCS = 1 ]]; then vendor/bin/phpcs -p --extensions=php --standard=vendor/cakephp/cakephp-codesniffer/CakePHP ./src ./tests; fi
 
+  - if [[ $PHPSTAN = 1 ]]; then vendor/bin/phpstan analyse -c phpstan.neon -l 5 src; fi
+
 after_success:
-- if [[ $DEFAULT = 1 && $TRAVIS_PHP_VERSION = 7.0 ]]; then bash <(curl -s https://codecov.io/bash); fi
+- if [[ $DEFAULT = 1 && $TRAVIS_PHP_VERSION = 7.1 ]]; then bash <(curl -s https://codecov.io/bash); fi
 
 notifications:
   email: false
diff --git a/composer.json b/composer.json
index 1872216..d59d0ca 100644
--- a/composer.json
+++ b/composer.json
@@ -22,10 +22,11 @@
         "issues":"https://github.com/ADmad/cakephp-jwt-auth/issues"
     },
     "require": {
-        "cakephp/cakephp": "^3.6",
+        "cakephp/cakephp": "^3.5",
         "firebase/php-jwt": "^5.0"
     },
     "require-dev": {
+        "cakephp/chronos": "^1.1",
         "phpunit/phpunit": "^5.7.14|^6.0"
     },
     "autoload": {
diff --git a/phpstan.neon b/phpstan.neon
new file mode 100644
index 0000000..3cf2159
--- /dev/null
+++ b/phpstan.neon
@@ -0,0 +1,3 @@
+parameters:
+    ignoreErrors:
+        - '#Call to an undefined method object::getConfig\(\)#'
diff --git a/src/Auth/JwtAuthenticate.php b/src/Auth/JwtAuthenticate.php
index 9afe4cb..9ea6a2d 100644
--- a/src/Auth/JwtAuthenticate.php
+++ b/src/Auth/JwtAuthenticate.php
@@ -88,7 +88,7 @@ class JwtAuthenticate extends BaseAuthenticate
      */
     public function __construct(ComponentRegistry $registry, $config)
     {
-        $this->setConfig([
+        $defaultConfig = [
             'header' => 'authorization',
             'prefix' => 'bearer',
             'parameter' => 'token',
@@ -96,7 +96,13 @@ public function __construct(ComponentRegistry $registry, $config)
             'fields' => ['username' => 'id'],
             'unauthenticatedException' => UnauthorizedException::class,
             'key' => null,
-        ]);
+        ];
+
+        if (!class_exists(UnauthorizedException::class, false)) {
+            $defaultConfig['unauthenticatedException'] = 'Cake\Network\Exception\UnauthorizedException';
+        }
+
+        $this->setConfig($defaultConfig);
 
         if (empty($config['allowedAlgs'])) {
             $config['allowedAlgs'] = ['HS256'];
@@ -177,7 +183,7 @@ public function getPayload($request = null)
     /**
      * Get token from header or query string.
      *
-     * @param \Cake\Network\Request|null $request Request object.
+     * @param \Cake\Http\ServerRequest|null $request Request object.
      *
      * @return string|null Token string if found else null.
      */
@@ -185,7 +191,7 @@ public function getToken($request = null)
     {
         $config = $this->_config;
 
-        if (!$request) {
+        if ($request === null) {
             return $this->_token;
         }
 
@@ -195,7 +201,10 @@ public function getToken($request = null)
         }
 
         if (!empty($this->_config['parameter'])) {
-            $this->_token = $request->getQuery($this->_config['parameter']);
+            $token = $request->getQuery($this->_config['parameter']);
+            if ($token !== null) {
+                $token = (string)$token;
+            }
         }
 
         return $this->_token;
@@ -246,7 +255,9 @@ public function unauthenticated(ServerRequest $request, Response $response)
             return;
         }
 
-        $message = $this->_error ? $this->_error->getMessage() : $this->_registry->Auth->_config['authError'];
+        $message = $this->_error
+            ? $this->_error->getMessage()
+            : $this->_registry->get('Auth')->getConfig('authError');
 
         $exception = new $this->_config['unauthenticatedException']($message);
         throw $exception;
diff --git a/tests/TestCase/Auth/JwtAuthenticateTest.php b/tests/TestCase/Auth/JwtAuthenticateTest.php
index cd76258..bc19dbd 100644
--- a/tests/TestCase/Auth/JwtAuthenticateTest.php
+++ b/tests/TestCase/Auth/JwtAuthenticateTest.php
@@ -4,6 +4,7 @@
 use ADmad\JwtAuth\Auth\JwtAuthenticate;
 use Cake\Controller\ComponentRegistry;
 use Cake\Core\Configure;
+use Cake\Http\Exception\UnauthorizedException;
 use Cake\Http\Response;
 use Cake\Http\ServerRequest;
 use Cake\I18n\Time;
@@ -253,13 +254,18 @@ public function testExceptionForInvalidToken()
     }
 
     /**
-     * @expectedException Cake\Http\Exception\UnauthorizedException
-     * @expectedExceptionMessage Auth error
+     * testUnauthenticated
      */
     public function testUnauthenticated()
     {
         $this->Registry->Auth->setConfig('authError', 'Auth error');
 
+        if (!class_exists(UnauthorizedException::class)) {
+            $exceptionClass = 'Cake\Network\Exception\UnauthorizedException';
+        }
+        $this->expectException($exceptionClass);
+        $this->expectExceptionMessage('Auth error');
+
         $result = $this->auth->unauthenticated(new ServerRequest(), $this->response);
     }