diff --git a/.github/workflows/unit.yml b/.github/workflows/unit.yml
index 1580678..6e279ca 100644
--- a/.github/workflows/unit.yml
+++ b/.github/workflows/unit.yml
@@ -27,6 +27,9 @@ jobs:
           - php: "8.3"
             mode: experimental
             os: ubuntu-20.04
+          - php: "8.4"
+            mode: experimental
+            os: ubuntu-20.04
       fail-fast: false
 
     runs-on: "${{ matrix.os }}"
diff --git a/.travis.yml b/.travis.yml
deleted file mode 100644
index 3ccd803..0000000
--- a/.travis.yml
+++ /dev/null
@@ -1,52 +0,0 @@
-dist: xenial
-
-language: php
-
-matrix:
-  include:
-    - php: 7.1
-    - php: 7.1
-      env: COMPOSER_FLAGS='--prefer-lowest'
-    - php: 7.2
-    - php: 7.2
-      env: COMPOSER_FLAGS='--prefer-lowest'
-    - php: 7.3
-    - php: 7.3
-      env: COMPOSER_FLAGS='--prefer-lowest'
-    - php: 7.4
-    - php: 7.4
-      env: COMPOSER_FLAGS='--prefer-lowest'
-    - php: 8.0
-    - php: 8.0
-      env: COMPOSER_FLAGS='--prefer-lowest'
-    - php: 8.1
-      env: ANALYSIS=1
-    - php: 8.1
-      env: COMPOSER_FLAGS='--prefer-lowest'
-    - php: nightly
-  allow_failures:
-    - php: nightly
-  fast_finish: true
-
-cache:
-  directories:
-    - $HOME/.composer
-
-install:
-  - COMPOSER_MEMORY_LIMIT=-1 travis_retry composer update $COMPOSER_FLAGS --no-suggest
-  - if [ $ANALYSIS == 1 ]; then travis_retry composer update --working-dir=./dev-tools --no-suggest; fi
-
-script:
-  - vendor/bin/simple-phpunit --verbose --coverage-clover=coverage.clover
-  - if [ $ANALYSIS == 1 ]; then ./dev-tools/analyse.sh || travis_terminate 1; fi
-
-after_script:
-  - sh -c 'if [ "$TRAVIS_PHP_VERSION" != "hhvm" ]; then wget https://scrutinizer-ci.com/ocular.phar && php ocular.phar code-coverage:upload --format=php-clover coverage.clover; fi;'
-
-notifications:
-  webhooks:
-    urls:
-      - https://webhooks.gitter.im/e/fc8ccb3e96abeb0fdc95
-    on_success: change
-    on_failure: always
-    on_start: never
diff --git a/composer.json b/composer.json
index 59efdf6..c6ae6ae 100644
--- a/composer.json
+++ b/composer.json
@@ -19,7 +19,7 @@
         }
     ],
     "require": {
-        "php": "~8.0.0 || ~8.1.0 || ~8.2.0 || ~8.3.0",
+        "php": "~8.0.0 || ~8.1.0 || ~8.2.0 || ~8.3.0 || ~8.4.0",
         "ext-mbstring": "*"
     },
     "conflict": {
diff --git a/src/Slugify.php b/src/Slugify.php
index c9f9e73..2eee4e5 100644
--- a/src/Slugify.php
+++ b/src/Slugify.php
@@ -80,7 +80,7 @@ class Slugify implements SlugifyInterface
      * @param array                 $options
      * @param RuleProviderInterface $provider
      */
-    public function __construct(array $options = [], RuleProviderInterface $provider = null)
+    public function __construct(array $options = [], ?RuleProviderInterface $provider = null)
     {
         $this->options  = array_merge($this->options, $options);
         $this->provider = $provider ? $provider : new DefaultRuleProvider();