diff --git a/.php-cs-fixer.dist.php b/.php-cs-fixer.dist.php
index db9e4a1..8f68dc8 100644
--- a/.php-cs-fixer.dist.php
+++ b/.php-cs-fixer.dist.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 return (new PhpCsFixer\Config())
     ->setRules([
         '@PHP7x1Migration' => true,
@@ -10,6 +12,7 @@
         'native_constant_invocation' => ['strict' => false],
         'nullable_type_declaration_for_default_null_value' => true,
         'modernize_strpos' => true,
+        'declare_strict_types' => ['strategy' => 'enforce'],
     ])
     ->setRiskyAllowed(true)
     ->setFinder(
diff --git a/composer.json b/composer.json
index 90ecd66..e36cfb7 100644
--- a/composer.json
+++ b/composer.json
@@ -23,7 +23,7 @@
         "symfony/console": "^7 || ^8"
     },
     "require-dev": {
-        "friendsofphp/php-cs-fixer": "3.92.5",
+        "friendsofphp/php-cs-fixer": "3.95.1",
         "phpunit/phpunit": "^11 || ^12 || ^13",
         "guzzlehttp/guzzle": "^7.0",
         "humbug/box": "^4.6",
diff --git a/src/Initiator.php b/src/Initiator.php
index 7d94133..2e0e614 100644
--- a/src/Initiator.php
+++ b/src/Initiator.php
@@ -1,5 +1,7 @@
 <?php
 
+declare(strict_types=1);
+
 namespace Deviantintegral\Har;
 
 use JMS\Serializer\Annotation as Serializer;
diff --git a/src/Log.php b/src/Log.php
index 6717250..fd5b03f 100644
--- a/src/Log.php
+++ b/src/Log.php
@@ -224,11 +224,11 @@ public function __clone(): void
 
         // Deep clone arrays of objects
         if (isset($this->pages)) {
-            $this->pages = array_map(fn (Page $page) => clone $page, $this->pages);
+            $this->pages = array_map(static fn (Page $page) => clone $page, $this->pages);
         }
 
         if (isset($this->entries)) {
-            $this->entries = array_map(fn (Entry $entry) => clone $entry, $this->entries);
+            $this->entries = array_map(static fn (Entry $entry) => clone $entry, $this->entries);
         }
     }
 }
diff --git a/src/Serializer.php b/src/Serializer.php
index f3271de..452a3ad 100644
--- a/src/Serializer.php
+++ b/src/Serializer.php
@@ -25,7 +25,7 @@ public function getSerializerBuilder(): SerializerBuilder
         $builder = SerializerBuilder::create()
           ->setPropertyNamingStrategy(new IdenticalPropertyNamingStrategy())
           ->configureHandlers(
-              function (HandlerRegistryInterface $registry) {
+              static function (HandlerRegistryInterface $registry) {
                   $registry->registerSubscribingHandler(
                       new DateFormatInterfaceHandler(Log::ISO_8601_MICROSECONDS)
                   );
diff --git a/tests/src/Unit/Handler/TruncatingDateTimeHandlerTest.php b/tests/src/Unit/Handler/TruncatingDateTimeHandlerTest.php
index 47cd31d..d2ebfe7 100644
--- a/tests/src/Unit/Handler/TruncatingDateTimeHandlerTest.php
+++ b/tests/src/Unit/Handler/TruncatingDateTimeHandlerTest.php
@@ -46,7 +46,7 @@ public function testGetSubscribingMethods(): void
         $this->assertContains('xml', $formats);
 
         // Verify method names are correctly formed for DateTimeInterface
-        $dateTimeInterfaceMethods = array_filter($methods, fn ($m) => 'DateTimeInterface' === $m['type']);
+        $dateTimeInterfaceMethods = array_filter($methods, static fn ($m) => 'DateTimeInterface' === $m['type']);
         $methodNames = array_column($dateTimeInterfaceMethods, 'method');
 
         // Method names should be deserializeDateTimeFromJson and deserializeDateTimeFromXml
diff --git a/tests/src/Unit/HarTest.php b/tests/src/Unit/HarTest.php
index e10d050..88520be 100644
--- a/tests/src/Unit/HarTest.php
+++ b/tests/src/Unit/HarTest.php
@@ -109,7 +109,7 @@ private function removeCustomFields(array &$a): void
             }
         }
 
-        $a = array_filter($a, function ($key): bool {
+        $a = array_filter($a, static function ($key): bool {
             return !\is_string($key) || !str_starts_with($key, '_');
         }, \ARRAY_FILTER_USE_KEY);
     }
diff --git a/tests/src/Unit/PostDataTest.php b/tests/src/Unit/PostDataTest.php
index 9544bfb..2893980 100644
--- a/tests/src/Unit/PostDataTest.php
+++ b/tests/src/Unit/PostDataTest.php
@@ -232,7 +232,7 @@ public function testGetBodySizeWithoutParamsDoesNotError(): void
 
         // Set up error handler to catch any warnings
         $warningTriggered = false;
-        $previousHandler = set_error_handler(function ($errno, $errstr) use (&$warningTriggered) {
+        $previousHandler = set_error_handler(static function ($errno, $errstr) use (&$warningTriggered) {
             if (str_contains($errstr, 'foreach') || str_contains($errstr, 'null')) {
                 $warningTriggered = true;
             }
diff --git a/tests/src/Unit/RequestTest.php b/tests/src/Unit/RequestTest.php
index de2eb09..d74c5bc 100644
--- a/tests/src/Unit/RequestTest.php
+++ b/tests/src/Unit/RequestTest.php
@@ -107,7 +107,7 @@ public function testFromPsr7ServerRequest(): void
 
         // Verify headers
         $headers = $har_request->getHeaders();
-        $headerNames = array_map(fn ($h) => $h->getName(), $headers);
+        $headerNames = array_map(static fn ($h) => $h->getName(), $headers);
         $this->assertContains('Host', $headerNames);
         $this->assertContains('Accept', $headerNames);