diff --git a/.gitattributes b/.gitattributes
index 709120a..63c0ce0 100644
--- a/.gitattributes
+++ b/.gitattributes
@@ -11,4 +11,14 @@
 # @link       https://github.com/JBZoo/Less
 #
 
+/.phan               export-ignore
+/build               export-ignore
+/tests               export-ignore
+/.editorconfig       export-ignore
+/.gitattributes      export-ignore
+/.gitignore          export-ignore
+/.travis.yml         export-ignore
+/phpunit.xml.dist    export-ignore
+/Makefile            export-ignore
+
 * text eol=lf
diff --git a/.phan/config.php b/.phan/config.php
index d2ced60..7bf5b18 100644
--- a/.phan/config.php
+++ b/.phan/config.php
@@ -13,6 +13,8 @@
  * @link       https://github.com/JBZoo/Less
  */
 
+declare(strict_types=1);
+
 $default = include __DIR__ . '/../vendor/jbzoo/codestyle/src/phan/default.php';
 
 return array_merge($default, [
diff --git a/.travis.yml b/.travis.yml
index 48e20a2..90cfec8 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -19,6 +19,14 @@ php:
   - 7.2
   - 7.3
   - 7.4
+  - 8.0
+  - nightly
+
+jobs:
+  fast_finish: true
+  allow_failures:
+    - php: 8.0
+    - php: nightly
 
 env:
   matrix:
diff --git a/README.md b/README.md
index df65b77..6e7dbad 100644
--- a/README.md
+++ b/README.md
@@ -1,6 +1,6 @@
 # JBZoo / Less
 
-[![Build Status](https://travis-ci.org/JBZoo/Less.svg)](https://travis-ci.org/JBZoo/Less)    [![Coverage Status](https://coveralls.io/repos/JBZoo/Less/badge.svg)](https://coveralls.io/github/JBZoo/Less)    [![Psalm Coverage](https://shepherd.dev/github/JBZoo/Less/coverage.svg)](https://shepherd.dev/github/JBZoo/Less)    
+[![Build Status](https://travis-ci.org/JBZoo/Less.svg)](https://travis-ci.org/JBZoo/Less)    [![Coverage Status](https://coveralls.io/repos/JBZoo/Less/badge.svg)](https://coveralls.io/github/JBZoo/Less)    [![Psalm Coverage](https://shepherd.dev/github/JBZoo/Less/coverage.svg)](https://shepherd.dev/github/JBZoo/Less)    [![PHP Strict Types](https://img.shields.io/badge/strict__types-%3D1-brightgreen)](https://www.php.net/manual/en/language.types.declarations.php#language.types.declarations.strict)    
 [![Stable Version](https://poser.pugx.org/jbzoo/less/version)](https://packagist.org/packages/jbzoo/less)    [![Latest Unstable Version](https://poser.pugx.org/jbzoo/less/v/unstable)](https://packagist.org/packages/jbzoo/less)    [![Dependents](https://poser.pugx.org/jbzoo/less/dependents)](https://packagist.org/packages/jbzoo/less/dependents?order_by=downloads)    [![GitHub Issues](https://img.shields.io/github/issues/jbzoo/less)](https://github.com/JBZoo/Less/issues)    [![Total Downloads](https://poser.pugx.org/jbzoo/less/downloads)](https://packagist.org/packages/jbzoo/less/stats)    [![GitHub License](https://img.shields.io/github/license/jbzoo/less)](https://github.com/JBZoo/Less/blob/master/LICENSE)
 
 
diff --git a/composer.json b/composer.json
index 5989674..2012238 100644
--- a/composer.json
+++ b/composer.json
@@ -18,13 +18,13 @@
     "require"           : {
         "php"                : ">=7.2",
 
-        "jbzoo/data"         : "^4.1.3",
-        "jbzoo/utils"        : "^4.2.3",
+        "jbzoo/data"         : "^4.2.0",
+        "jbzoo/utils"        : "^4.3.0",
         "wikimedia/less.php" : "^3.1.0"
     },
 
     "require-dev"       : {
-        "jbzoo/toolbox-dev" : "^2.6.2"
+        "jbzoo/toolbox-dev" : "^2.10.0"
     },
 
     "autoload"          : {
diff --git a/src/Cache.php b/src/Cache.php
index b29b735..8d88a16 100644
--- a/src/Cache.php
+++ b/src/Cache.php
@@ -13,6 +13,8 @@
  * @link       https://github.com/JBZoo/Less
  */
 
+declare(strict_types=1);
+
 namespace JBZoo\Less;
 
 use JBZoo\Data\Data;
@@ -27,7 +29,7 @@
  * Class Cache
  * @package JBZoo\Less
  */
-class Cache
+final class Cache
 {
     /**
      * @var int
diff --git a/src/Exception.php b/src/Exception.php
index 99abb94..02bc8a9 100644
--- a/src/Exception.php
+++ b/src/Exception.php
@@ -13,6 +13,8 @@
  * @link       https://github.com/JBZoo/Less
  */
 
+declare(strict_types=1);
+
 namespace JBZoo\Less;
 
 /**
diff --git a/src/Gpeasy.php b/src/Gpeasy.php
index 1b025b3..f2d1aae 100644
--- a/src/Gpeasy.php
+++ b/src/Gpeasy.php
@@ -13,6 +13,8 @@
  * @link       https://github.com/JBZoo/Less
  */
 
+declare(strict_types=1);
+
 namespace JBZoo\Less;
 
 use JBZoo\Data\Data;
@@ -24,7 +26,7 @@
  * Class Gpeasy
  * @package JBZoo\Less
  */
-class Gpeasy
+final class Gpeasy
 {
     /**
      * @var Less_Parser|null
diff --git a/src/Less.php b/src/Less.php
index fec2c11..1c07ca1 100644
--- a/src/Less.php
+++ b/src/Less.php
@@ -13,6 +13,8 @@
  * @link       https://github.com/JBZoo/Less
  */
 
+declare(strict_types=1);
+
 namespace JBZoo\Less;
 
 use JBZoo\Data\Data;
@@ -25,7 +27,7 @@
  * Class Less
  * @package JBZoo\Less
  */
-class Less
+final class Less
 {
     /**
      * @var array
diff --git a/tests/AbstractLessTest.php b/tests/AbstractLessTest.php
index d94fb37..e362b41 100644
--- a/tests/AbstractLessTest.php
+++ b/tests/AbstractLessTest.php
@@ -13,6 +13,8 @@
  * @link       https://github.com/JBZoo/Less
  */
 
+declare(strict_types=1);
+
 namespace JBZoo\PHPUnit;
 
 use JBZoo\Less\Less;
diff --git a/tests/DriverGpeasyTest.php b/tests/DriverGpeasyTest.php
index 368358f..9879794 100644
--- a/tests/DriverGpeasyTest.php
+++ b/tests/DriverGpeasyTest.php
@@ -13,6 +13,8 @@
  * @link       https://github.com/JBZoo/Less
  */
 
+declare(strict_types=1);
+
 namespace JBZoo\PHPUnit;
 
 /**
diff --git a/tests/LessCodestyleTest.php b/tests/LessCodestyleTest1.php
similarity index 83%
rename from tests/LessCodestyleTest.php
rename to tests/LessCodestyleTest1.php
index b1a1d7e..d92fa8f 100644
--- a/tests/LessCodestyleTest.php
+++ b/tests/LessCodestyleTest1.php
@@ -13,15 +13,18 @@
  * @link       https://github.com/JBZoo/Less
  */
 
+declare(strict_types=1);
+
 namespace JBZoo\PHPUnit;
 
 /**
  * Class LessCodestyleTest
  * @package JBZoo\PHPUnit
  */
-class LessCodestyleTest extends AbstractCopyrightTest
+class LessCopyrightTest extends AbstractCopyrightTest
 {
-    protected $packageName = "Less";
+    protected $packageName     = "Less";
+    protected $isPhpStrictType = true;
 
     protected function setUp(): void
     {
diff --git a/tests/LessComposerTest.php b/tests/LessComposerTest.php
index 176ee3c..d602162 100644
--- a/tests/LessComposerTest.php
+++ b/tests/LessComposerTest.php
@@ -13,6 +13,8 @@
  * @link       https://github.com/JBZoo/Less
  */
 
+declare(strict_types=1);
+
 namespace JBZoo\PHPUnit;
 
 /**
diff --git a/tests/LessCopyrightsTest.php b/tests/LessCopyrightsTest.php
index be7d3d8..819cbef 100644
--- a/tests/LessCopyrightsTest.php
+++ b/tests/LessCopyrightsTest.php
@@ -13,13 +13,15 @@
  * @link       https://github.com/JBZoo/Less
  */
 
+declare(strict_types=1);
+
 namespace JBZoo\PHPUnit;
 
 /**
- * Class LessCopyrightsTest
+ * Class LessCodestyleTest
  * @package JBZoo\PHPUnit
  */
-class LessCopyrightsTest extends AbstractCodestyleTest
+class LessCodestyleTest extends AbstractCodestyleTest
 {
 
 }
diff --git a/tests/LessReadmeTest.php b/tests/LessReadmeTest.php
index f9830a1..cda0d12 100644
--- a/tests/LessReadmeTest.php
+++ b/tests/LessReadmeTest.php
@@ -13,6 +13,8 @@
  * @link       https://github.com/JBZoo/Less
  */
 
+declare(strict_types=1);
+
 namespace JBZoo\PHPUnit;
 
 /**
@@ -23,4 +25,10 @@
 class LessReadmeTest extends AbstractReadmeTest
 {
     protected $packageName = 'Less';
+
+    protected function setUp(): void
+    {
+        parent::setUp();
+        $this->params['strict_types'] = true;
+    }
 }
diff --git a/tests/autoload.php b/tests/autoload.php
index 577d475..1dc6ddd 100644
--- a/tests/autoload.php
+++ b/tests/autoload.php
@@ -13,6 +13,8 @@
  * @link       https://github.com/JBZoo/Less
  */
 
+declare(strict_types=1);
+
 if (!defined('ROOT_PATH')) { // for PHPUnit process isolation
     define('ROOT_PATH', realpath('.'));
 }