diff --git a/.github/workflows/build.yml b/.github/workflows/build.yml
index 8a60024..9241d18 100644
--- a/.github/workflows/build.yml
+++ b/.github/workflows/build.yml
@@ -20,6 +20,7 @@ jobs:
           - "8.1"
           - "8.2"
           - "8.3"
+          - "8.4"
         dependencies:
           - lowest
           - highest
diff --git a/composer.json b/composer.json
index 254303b..b703b4a 100644
--- a/composer.json
+++ b/composer.json
@@ -14,7 +14,7 @@
     }
   ],
   "require": {
-    "php": "~8.1.0 || ~8.2.0 || ~8.3.0",
+    "php": "~8.1.0 || ~8.2.0 || ~8.3.0 || ~8.4.0",
     "ext-json": "*",
     "ext-intl": "*"
   },
diff --git a/docker-compose.yml b/docker-compose.yml
index a3e8597..25a7f68 100644
--- a/docker-compose.yml
+++ b/docker-compose.yml
@@ -22,3 +22,10 @@ services:
     volumes:
       - .:/app
     working_dir: /app
+  php8.4:
+    build:
+      context: .
+      dockerfile: php-8.4.Dockerfile
+    volumes:
+      - .:/app
+    working_dir: /app
diff --git a/php-8.4.Dockerfile b/php-8.4.Dockerfile
new file mode 100644
index 0000000..8406b08
--- /dev/null
+++ b/php-8.4.Dockerfile
@@ -0,0 +1,27 @@
+FROM php:8.4-cli
+
+RUN apt-get update &&  apt-get install -y \
+      zip \
+      git \
+      wget \
+      gpg \
+      libicu-dev && \
+    pecl install xdebug && \
+    docker-php-ext-enable xdebug && \
+    docker-php-ext-configure intl --enable-intl && \
+    docker-php-ext-install intl pcntl && \
+    echo "xdebug.mode = develop,coverage,debug" >> "$PHP_INI_DIR/conf.d/docker-php-ext-xdebug.ini"
+
+ENV COMPOSER_ALLOW_SUPERUSER=1 \
+    COMPOSER_PROCESS_TIMEOUT=1200
+
+RUN curl --silent --show-error https://getcomposer.org/installer | php -- \
+      --install-dir=/usr/bin --filename=composer && \
+    git config --global --add safe.directory "*"
+
+RUN wget -O phive.phar https://phar.io/releases/phive.phar && \
+    wget -O phive.phar.asc https://phar.io/releases/phive.phar.asc && \
+    gpg --keyserver hkps://keys.openpgp.org --recv-keys 0x9D8A98B29B2D5D79 && \
+    gpg --verify phive.phar.asc phive.phar && \
+    chmod +x phive.phar && \
+    mv phive.phar /usr/local/bin/phive \
diff --git a/vendor-bin/psalm/composer.json b/vendor-bin/psalm/composer.json
index 83fd035..6191591 100644
--- a/vendor-bin/psalm/composer.json
+++ b/vendor-bin/psalm/composer.json
@@ -1,7 +1,7 @@
 {
     "require-dev": {
-        "vimeo/psalm": "^5.21.1",
-        "psalm/plugin-phpunit": "^0.18.4"
+        "vimeo/psalm": "dev-master",
+        "psalm/plugin-phpunit": "^0.19.0"
     },
     "conflict": {
         "netresearch/jsonmapper": "<4.4.1"