diff --git a/.github/workflows/ci.yml b/.github/workflows/ci.yml
index 594308d..591f695 100644
--- a/.github/workflows/ci.yml
+++ b/.github/workflows/ci.yml
@@ -17,7 +17,6 @@ jobs:
         php-version:
           - "8.3"
           - "8.2"
-          - "8.1"
 
         dependencies:
           - "highest"
@@ -69,7 +68,7 @@ jobs:
           php-${{ matrix.php-version }}-deps-${{ matrix.dependencies }}
 
     - name: Remove PHP-CS-Fixer if not called
-      if: matrix.php-version != '8.1' || matrix.dependencies != 'highest'
+      if: matrix.php-version != '8.2' || matrix.dependencies != 'highest'
       run: composer remove --dev --no-update "friendsofphp/php-cs-fixer";
 
     - name: Install dependencies (low)
@@ -100,7 +99,7 @@ jobs:
 
     - name: PHPUnit
       run: |
-        if [ "${{ matrix.php-version }}" = "8.1" ] && [ "${{ matrix.dependencies }}" = "highest" ]; then
+        if [ "${{ matrix.php-version }}" = "8.2" ] && [ "${{ matrix.dependencies }}" = "highest" ]; then
           php -dmemory_limit=-1 vendor/phpunit/phpunit/phpunit --exclude-group=efficiency;
           composer global require scrutinizer/ocular;
           ~/.composer/vendor/bin/ocular code-coverage:upload --format=php-clover build/coverage-phpunit/clover.xml;
@@ -110,7 +109,7 @@ jobs:
 
     - name: Behat
       run: |
-        if [ "${{ matrix.php-version }}" = "8.1" ] && [ "${{ matrix.dependencies }}" = "highest" ]; then
+        if [ "${{ matrix.php-version }}" = "8.2" ] && [ "${{ matrix.dependencies }}" = "highest" ]; then
           php -dmemory_limit=-1 vendor/behat/behat/bin/behat --strict;
           ~/.composer/vendor/bin/ocular code-coverage:upload --format=php-clover build/coverage-behat/clover.xml;
         else
@@ -118,7 +117,7 @@ jobs:
         fi;
 
     - name: Check code style
-      if: matrix.php-version == '8.1' && matrix.dependencies == 'highest'
+      if: matrix.php-version == '8.2' && matrix.dependencies == 'highest'
       run: vendor/bin/php-cs-fixer fix --verbose --dry-run --diff --allow-risky=yes --format=checkstyle | cs2pr
 
 
@@ -132,7 +131,6 @@ jobs:
         php-version:
           - "8.3"
           - "8.2"
-          - "8.1"
 
         dependencies:
           - "highest"
diff --git a/.php-cs-fixer.dist.php b/.php-cs-fixer.dist.php
index e4e0c50..a326455 100644
--- a/.php-cs-fixer.dist.php
+++ b/.php-cs-fixer.dist.php
@@ -14,6 +14,7 @@
         '@Symfony:risky' => true,
         '@PHP80Migration:risky' => true,
         '@PHP81Migration' => true,
+        '@PHP82Migration' => true,
         'concat_space' => ['spacing' => 'one'],
         'fopen_flags' => ['b_mode' => true],
         'native_function_invocation' => ['include' => ['@all']],
diff --git a/.scrutinizer.yml b/.scrutinizer.yml
index c276268..3e8c606 100644
--- a/.scrutinizer.yml
+++ b/.scrutinizer.yml
@@ -15,7 +15,7 @@ build:
   environment:
     # Languages
     php:
-      version: "8.1"
+      version: "8.2"
       ini:
         memory_limit: "-1"
 
diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0273abe..69bf415 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -14,7 +14,7 @@
    exceptions are disabled).
 
 ### Changed
- - Minimum PHP version is now 8.1
+ - Minimum PHP version is now 8.2
  - Exceptions are now in the `DVDoug\BoxPacker\Exception` namespace (previously `DVDoug\BoxPacker`)
  - The signature of the `canBePacked` method on the `ConstrainedPlacementItem` interface has been changed to replace the
    first two arguments(`Box $box`, `PackedItemList $alreadyPackedItems`) with `PackedBox $packedBox`. This allows
diff --git a/composer.json b/composer.json
index a214a9e..c7d74a3 100644
--- a/composer.json
+++ b/composer.json
@@ -12,16 +12,16 @@
     ],
     "license": "MIT",
     "require": {
-        "php": "^8.1",
+        "php": "^8.2",
         "ext-json": "*",
         "psr/log": "^1.0||^2.0||^3.0"
     },
     "require-dev": {
         "behat/behat": "^3.13",
         "dvdoug/behat-code-coverage": "^5.3.1",
-        "friendsofphp/php-cs-fixer": "^3.22.0",
-        "monolog/monolog": "^3.4",
-        "phpunit/phpunit": "^10.2"
+        "friendsofphp/php-cs-fixer": "^3.38.2",
+        "monolog/monolog": "^3.5",
+        "phpunit/phpunit": "^10.4"
     },
     "config": {
         "preferred-install": {
@@ -38,7 +38,7 @@
     },
     "extra": {
         "branch-alias": {
-            "dev-master": "4.0-dev"
+            "dev-master": "4.x-dev"
         }
     }
 }
diff --git a/docs/installation.rst b/docs/installation.rst
index 4801dc0..1d54301 100644
--- a/docs/installation.rst
+++ b/docs/installation.rst
@@ -13,7 +13,7 @@ If you don't want to use Composer, the code is available to download from `GitHu
 
 Requirements
 ------------
-BoxPacker v4 is compatible with PHP 8.1+
+BoxPacker v4 is compatible with PHP 8.2+
 
 Versioning
 ----------
diff --git a/src/PackedBox.php b/src/PackedBox.php
index 6c6f9be..f0dbb28 100644
--- a/src/PackedBox.php
+++ b/src/PackedBox.php
@@ -29,11 +29,11 @@
 /**
  * A "box" with items.
  */
-class PackedBox implements JsonSerializable
+readonly class PackedBox implements JsonSerializable
 {
-    protected readonly int $itemWeight;
+    protected int $itemWeight;
 
-    protected readonly float $volumeUtilisation;
+    protected float $volumeUtilisation;
 
     /**
      * Get packed weight.
@@ -202,7 +202,7 @@ public function generateVisualisationURL(): string
         return 'https://boxpacker.io/en/master/visualiser.html?packing=' . json_encode($data, flags: JSON_THROW_ON_ERROR | JSON_NUMERIC_CHECK | JSON_UNESCAPED_UNICODE | JSON_UNESCAPED_SLASHES);
     }
 
-    public function __construct(public readonly Box $box, public readonly PackedItemList $items)
+    public function __construct(public Box $box, public PackedItemList $items)
     {
         assert($this->assertPackingCompliesWithRealWorld());
     }
diff --git a/src/PackedItem.php b/src/PackedItem.php
index 14168d4..5991092 100644
--- a/src/PackedItem.php
+++ b/src/PackedItem.php
@@ -15,18 +15,18 @@
 /**
  * A packed item.
  */
-class PackedItem implements JsonSerializable
+readonly class PackedItem implements JsonSerializable
 {
-    public readonly int $volume;
+    public int $volume;
 
     public function __construct(
-        public readonly Item $item,
-        public readonly int $x,
-        public readonly int $y,
-        public readonly int $z,
-        public readonly int $width,
-        public readonly int $length,
-        public readonly int $depth
+        public Item $item,
+        public int $x,
+        public int $y,
+        public int $z,
+        public int $width,
+        public int $length,
+        public int $depth
     ) {
     }
 
diff --git a/src/WorkingVolume.php b/src/WorkingVolume.php
index f2d3a4c..757c39a 100644
--- a/src/WorkingVolume.php
+++ b/src/WorkingVolume.php
@@ -14,13 +14,13 @@
  * Class WorkingVolume.
  * @internal
  */
-class WorkingVolume implements Box, JsonSerializable
+readonly class WorkingVolume implements Box, JsonSerializable
 {
     public function __construct(
-        private readonly int $width,
-        private readonly int $length,
-        private readonly int $depth,
-        private readonly int $maxWeight
+        private int $width,
+        private int $length,
+        private int $depth,
+        private int $maxWeight
     ) {
     }