diff --git a/.github/workflows/ci.yaml b/.github/workflows/ci.yaml
index c0c5951..cbbe6dd 100644
--- a/.github/workflows/ci.yaml
+++ b/.github/workflows/ci.yaml
@@ -2,14 +2,13 @@ name: ci
 
 on:
   push:
-    branches:
-      - main
+
 jobs:
   run:
     runs-on: ubuntu-latest
     strategy:
       matrix:
-        php-versions: ["8.2", "8.3", "8.4"]
+        php-versions: ["8.2", "8.3", "8.4", "8.5"]
     name: PHP ${{ matrix.php-versions }}
     steps:
       - name: Checkout
diff --git a/composer.json b/composer.json
index 2e17fcc..94d44f7 100644
--- a/composer.json
+++ b/composer.json
@@ -19,9 +19,9 @@
     },
     "require-dev": {
         "laravel/pint": "^1.17.3",
-        "pestphp/pest": "^2.35.1",
-        "phpstan/phpstan": "^1.12.2",
-        "rector/rector": "^1.2.4",
+        "pestphp/pest": "^v3.8.6",
+        "phpstan/phpstan": "^2.2.5",
+        "rector/rector": "^2.5.3",
         "symfony/var-dumper": "^6.4|^7.1.4"
     },
     "autoload": {
diff --git a/src/Nodes/ArrayNode.php b/src/Nodes/ArrayNode.php
index 72a0abf..7bab883 100644
--- a/src/Nodes/ArrayNode.php
+++ b/src/Nodes/ArrayNode.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml\Nodes;
 
 /**
diff --git a/src/Nodes/ArrayTableNode.php b/src/Nodes/ArrayTableNode.php
index d9108fe..e621fad 100644
--- a/src/Nodes/ArrayTableNode.php
+++ b/src/Nodes/ArrayTableNode.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml\Nodes;
 
 /**
diff --git a/src/Nodes/BareNode.php b/src/Nodes/BareNode.php
index 6214cdd..033d827 100644
--- a/src/Nodes/BareNode.php
+++ b/src/Nodes/BareNode.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml\Nodes;
 
 /**
diff --git a/src/Nodes/BooleanNode.php b/src/Nodes/BooleanNode.php
index c2821f3..6f9bab4 100644
--- a/src/Nodes/BooleanNode.php
+++ b/src/Nodes/BooleanNode.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml\Nodes;
 
 /**
diff --git a/src/Nodes/FloatNode.php b/src/Nodes/FloatNode.php
index bcc8212..2651223 100644
--- a/src/Nodes/FloatNode.php
+++ b/src/Nodes/FloatNode.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml\Nodes;
 
 /**
diff --git a/src/Nodes/InlineTableNode.php b/src/Nodes/InlineTableNode.php
index c3e6a94..f346b48 100644
--- a/src/Nodes/InlineTableNode.php
+++ b/src/Nodes/InlineTableNode.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml\Nodes;
 
 /**
diff --git a/src/Nodes/IntegerNode.php b/src/Nodes/IntegerNode.php
index 14a21f1..f0a3133 100644
--- a/src/Nodes/IntegerNode.php
+++ b/src/Nodes/IntegerNode.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml\Nodes;
 
 /**
diff --git a/src/Nodes/KeyNode.php b/src/Nodes/KeyNode.php
index eb078ba..0a2f2ff 100644
--- a/src/Nodes/KeyNode.php
+++ b/src/Nodes/KeyNode.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml\Nodes;
 
 /**
diff --git a/src/Nodes/KeyValuePairNode.php b/src/Nodes/KeyValuePairNode.php
index 9487780..4c4268d 100644
--- a/src/Nodes/KeyValuePairNode.php
+++ b/src/Nodes/KeyValuePairNode.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml\Nodes;
 
 /**
diff --git a/src/Nodes/LocalDateNode.php b/src/Nodes/LocalDateNode.php
index 7dbe237..8195613 100644
--- a/src/Nodes/LocalDateNode.php
+++ b/src/Nodes/LocalDateNode.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml\Nodes;
 
 use Devium\Toml\TomlLocalDate;
diff --git a/src/Nodes/LocalDateTimeNode.php b/src/Nodes/LocalDateTimeNode.php
index cdc71f8..ab58e06 100644
--- a/src/Nodes/LocalDateTimeNode.php
+++ b/src/Nodes/LocalDateTimeNode.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml\Nodes;
 
 use Devium\Toml\TomlLocalDateTime;
diff --git a/src/Nodes/LocalTimeNode.php b/src/Nodes/LocalTimeNode.php
index b6ecba7..741eef9 100644
--- a/src/Nodes/LocalTimeNode.php
+++ b/src/Nodes/LocalTimeNode.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml\Nodes;
 
 use Devium\Toml\TomlLocalTime;
diff --git a/src/Nodes/Node.php b/src/Nodes/Node.php
index 74d7587..caa1b2c 100644
--- a/src/Nodes/Node.php
+++ b/src/Nodes/Node.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml\Nodes;
 
 /**
diff --git a/src/Nodes/NumericNode.php b/src/Nodes/NumericNode.php
index 2294d7f..1790e19 100644
--- a/src/Nodes/NumericNode.php
+++ b/src/Nodes/NumericNode.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml\Nodes;
 
 /**
diff --git a/src/Nodes/OffsetDateTimeNode.php b/src/Nodes/OffsetDateTimeNode.php
index 05d46c8..4164032 100644
--- a/src/Nodes/OffsetDateTimeNode.php
+++ b/src/Nodes/OffsetDateTimeNode.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml\Nodes;
 
 use Devium\Toml\TomlDateTime;
diff --git a/src/Nodes/RootTableNode.php b/src/Nodes/RootTableNode.php
index 35e142b..ee4deb4 100644
--- a/src/Nodes/RootTableNode.php
+++ b/src/Nodes/RootTableNode.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml\Nodes;
 
 /**
diff --git a/src/Nodes/StringNode.php b/src/Nodes/StringNode.php
index 1587a08..8089d93 100644
--- a/src/Nodes/StringNode.php
+++ b/src/Nodes/StringNode.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml\Nodes;
 
 /**
diff --git a/src/Nodes/TableNode.php b/src/Nodes/TableNode.php
index 022f2b7..a2fd8e4 100644
--- a/src/Nodes/TableNode.php
+++ b/src/Nodes/TableNode.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml\Nodes;
 
 /**
diff --git a/src/Nodes/TomlDateTimeNode.php b/src/Nodes/TomlDateTimeNode.php
index b12630b..45a49ba 100644
--- a/src/Nodes/TomlDateTimeNode.php
+++ b/src/Nodes/TomlDateTimeNode.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml\Nodes;
 
 /**
diff --git a/src/Nodes/ValuableNode.php b/src/Nodes/ValuableNode.php
index 1c033ff..2ea4782 100644
--- a/src/Nodes/ValuableNode.php
+++ b/src/Nodes/ValuableNode.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml\Nodes;
 
 /**
diff --git a/src/Toml.php b/src/Toml.php
index 3a28b4b..eb64ade 100644
--- a/src/Toml.php
+++ b/src/Toml.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml;
 
 use stdClass;
diff --git a/src/TomlDateTimeInterface.php b/src/TomlDateTimeInterface.php
index d547a25..01393b1 100644
--- a/src/TomlDateTimeInterface.php
+++ b/src/TomlDateTimeInterface.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml;
 
 interface TomlDateTimeInterface {}
diff --git a/src/TomlDecoder.php b/src/TomlDecoder.php
index aecfe51..9e4e6d2 100644
--- a/src/TomlDecoder.php
+++ b/src/TomlDecoder.php
@@ -35,7 +35,7 @@ protected static function toArray(mixed $object): mixed
         }
 
         if (is_array($object) || is_object($object)) {
-            return array_map(static fn ($value) => self::toArray($value), (array) $object);
+            return array_map(self::toArray(...), (array) $object);
         }
 
         return $object;
diff --git a/src/TomlEncoder.php b/src/TomlEncoder.php
index 8a02a5a..06e7446 100644
--- a/src/TomlEncoder.php
+++ b/src/TomlEncoder.php
@@ -83,7 +83,7 @@ protected static function stringifyTable(object $obj, string $prefix = ''): stri
             }
 
             $type = self::extendedTypeOf($obj->{$k});
-            $key = preg_match(self::BARE_KEY, $k) ? $k : self::formatString($k);
+            $key = preg_match(self::BARE_KEY, (string) $k) ? $k : self::formatString($k);
             if ($type === 'array' && self::isArrayOfTables($obj->{$k})) {
                 $tables .= self::stringifyArrayTable($obj->{$k}, $prefix !== '' && $prefix !== '0' ? "$prefix.$key" : $key);
             } elseif ($type === 'object') {
@@ -205,7 +205,7 @@ protected static function stringifyInlineTable(array|stdClass $obj): string
             if ($i !== 0) {
                 $res .= ', ';
             }
-            $res .= preg_match(self::BARE_KEY, $k) ? $k : self::formatString($k);
+            $res .= preg_match(self::BARE_KEY, (string) $k) ? $k : self::formatString($k);
             $res .= ' = ';
             $res .= self::stringifyValue($obj->{$k});
         }
diff --git a/src/TomlInputIterator.php b/src/TomlInputIterator.php
index a1c8802..279e47e 100644
--- a/src/TomlInputIterator.php
+++ b/src/TomlInputIterator.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml;
 
 /**
diff --git a/src/TomlLocalDate.php b/src/TomlLocalDate.php
index ab69c70..f8b9abf 100644
--- a/src/TomlLocalDate.php
+++ b/src/TomlLocalDate.php
@@ -19,7 +19,7 @@ public static function fromString($value): self
             throw new TomlError("invalid local date format \"$value\"");
         }
 
-        [$year, $month, $day] = array_map('intval', explode('-', (string) $value));
+        [$year, $month, $day] = array_map(intval(...), explode('-', (string) $value));
 
         if (! self::isYear($year) || ! self::isMonth($month) || ! self::isDay($day)) {
             throw new TomlError("invalid local date format \"$value\"");
diff --git a/src/TomlLocalTime.php b/src/TomlLocalTime.php
index 7440cf6..c2b17e0 100644
--- a/src/TomlLocalTime.php
+++ b/src/TomlLocalTime.php
@@ -25,8 +25,8 @@ public static function fromString($value): self
         }
 
         $components = explode(':', (string) $value);
-        [$hour, $minute] = array_map('intval', array_slice($components, 0, 2));
-        $p = array_map('intval', explode('.', $components[2]));
+        [$hour, $minute] = array_map(intval(...), array_slice($components, 0, 2));
+        $p = array_map(intval(...), explode('.', $components[2]));
         $second = $p[0];
         $millisecond = $p[1] ?? 0;
 
diff --git a/src/TomlNormalizer.php b/src/TomlNormalizer.php
index 8450332..283e269 100644
--- a/src/TomlNormalizer.php
+++ b/src/TomlNormalizer.php
@@ -82,7 +82,7 @@ public static function normalize(Nodes\Node $node): mixed
      */
     protected static function mapNormalize(array $items): array
     {
-        return array_map(static fn ($element) => self::normalize($element), $items);
+        return array_map(self::normalize(...), $items);
     }
 
     /**
diff --git a/src/TomlObject.php b/src/TomlObject.php
index c640233..754c8fe 100644
--- a/src/TomlObject.php
+++ b/src/TomlObject.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml;
 
 use ArrayObject;
diff --git a/src/TomlParser.php b/src/TomlParser.php
index dddc91e..19c0443 100644
--- a/src/TomlParser.php
+++ b/src/TomlParser.php
@@ -254,7 +254,7 @@ protected function dateOrDateTime(string $value): OffsetDateTimeNode|LocalDateTi
         );
         $value .= implode('', array_map(static fn (TomlToken $token) => $token->value, $tokens));
 
-        $lastTokenValue = strtolower($tokens[count($tokens) - 1]->value);
+        $lastTokenValue = strtolower((string) $tokens[count($tokens) - 1]->value);
 
         if (str_ends_with($lastTokenValue, 'z')) {
             return new OffsetDateTimeNode($this->parseDate($value));
@@ -429,7 +429,7 @@ protected function parseInteger(
             }
 
             $octalOrBinary = ($radix === 8 && $char === 'o') || ($radix === 2 && $char === 'b');
-            if (! ($i === 1 && $octalOrBinary) && ! $this->digitalChecks($radix, $char)) {
+            if (($i !== 1 || ! $octalOrBinary) && ! $this->digitalChecks($radix, $char)) {
                 break;
             }
 
diff --git a/src/TomlTag.php b/src/TomlTag.php
index 24bf70d..bea90d7 100644
--- a/src/TomlTag.php
+++ b/src/TomlTag.php
@@ -61,7 +61,7 @@ public static function tagObject(mixed $obj): array|stdClass
         }
 
         if (is_array($obj)) {
-            return array_map(static fn ($item) => self::tagObject($item), $obj);
+            return array_map(self::tagObject(...), $obj);
         }
 
         $tagged = new stdClass;
@@ -84,7 +84,7 @@ public static function tagObject(mixed $obj): array|stdClass
     public static function untagObject($obj)
     {
         if (is_array($obj)) {
-            return array_map(static fn ($item) => self::untagObject($item), $obj);
+            return array_map(self::untagObject(...), $obj);
         }
 
         if (property_exists($obj, 'type') && property_exists($obj, 'value') && count(get_object_vars($obj)) === 2) {
diff --git a/src/TomlTokenizer.php b/src/TomlTokenizer.php
index a0b3eab..e6d210f 100644
--- a/src/TomlTokenizer.php
+++ b/src/TomlTokenizer.php
@@ -355,7 +355,7 @@ protected function scanBasicString(): TomlToken
      */
     public function sequence(...$types): array
     {
-        return array_map(fn ($type) => $this->expect($type), $types);
+        return array_map($this->expect(...), $types);
     }
 
     /**
diff --git a/src/TomlUtils.php b/src/TomlUtils.php
index 50ea2ed..c98106f 100644
--- a/src/TomlUtils.php
+++ b/src/TomlUtils.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Devium\Toml;
 
 /**
diff --git a/src/helpers.php b/src/helpers.php
index 4cdce65..053be38 100644
--- a/src/helpers.php
+++ b/src/helpers.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use Devium\Toml\Toml;
 use Devium\Toml\TomlError;
 
diff --git a/tests/TestCase.php b/tests/TestCase.php
index cfb05b6..d42f312 100644
--- a/tests/TestCase.php
+++ b/tests/TestCase.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Tests;
 
 use PHPUnit\Framework\TestCase as BaseTestCase;
diff --git a/tests/Unit/TomlDecodeTest.php b/tests/Unit/TomlDecodeTest.php
index e0060be..ee17f27 100644
--- a/tests/Unit/TomlDecodeTest.php
+++ b/tests/Unit/TomlDecodeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use Devium\Toml\TomlError;
 
 it('can decode TOML',
diff --git a/tests/Unit/TomlEncodeTest.php b/tests/Unit/TomlEncodeTest.php
index e5e309d..3aa45f1 100644
--- a/tests/Unit/TomlEncodeTest.php
+++ b/tests/Unit/TomlEncodeTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use Devium\Toml\TomlError;
 
 it('can encode TOML',
diff --git a/tests/Unit/TomlErrorTest.php b/tests/Unit/TomlErrorTest.php
index f8628c5..3ed4a95 100644
--- a/tests/Unit/TomlErrorTest.php
+++ b/tests/Unit/TomlErrorTest.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 use Devium\Toml\TomlError;
 
 it('shows code block and caret',