diff --git a/composer.json b/composer.json
index 33eaea6..cc12d26 100644
--- a/composer.json
+++ b/composer.json
@@ -7,7 +7,7 @@
         "illuminate/support": "^12.0|^13.0",
         "jawira/case-converter": "^3.6",
         "nette/utils": "^4.1",
-        "sebastian/diff": "^6.0|^7.0",
+        "sebastian/diff": "^9.0",
         "symfony/config": "^7.4|^8.0",
         "symfony/console": "^7.4|^8.0",
         "symfony/dependency-injection": "^7.4|^8.0",
@@ -18,7 +18,7 @@
         "webonyx/graphql-php": "^15.34"
     },
     "require-dev": {
-        "pestphp/pest": "^4.7",
+        "pestphp/pest": "^5.3",
         "symfony/var-dumper": "^7.4|^8.0",
         "worksome/coding-style": "^6.0"
     },
diff --git a/src/Diff/CompleteUnifiedDiffOutputBuilderFactory.php b/src/Diff/CompleteUnifiedDiffOutputBuilderFactory.php
index 533701f..de57bcd 100644
--- a/src/Diff/CompleteUnifiedDiffOutputBuilderFactory.php
+++ b/src/Diff/CompleteUnifiedDiffOutputBuilderFactory.php
@@ -4,21 +4,18 @@
 
 namespace Worksome\Graphlint\Diff;
 
-use ReflectionProperty;
-use SebastianBergmann\Diff\Output\UnifiedDiffOutputBuilder;
+use SebastianBergmann\Diff\Output\StrictUnifiedDiffOutputBuilder;
 
 /** @api */
 final class CompleteUnifiedDiffOutputBuilderFactory
 {
     /** @api */
-    public function create(): UnifiedDiffOutputBuilder
+    public function create(): StrictUnifiedDiffOutputBuilder
     {
-        $unifiedDiffOutputBuilder = new UnifiedDiffOutputBuilder('');
-
-        $contextLines = new ReflectionProperty($unifiedDiffOutputBuilder, 'contextLines');
-
-        $contextLines->setValue($unifiedDiffOutputBuilder, 10000);
-
-        return $unifiedDiffOutputBuilder;
+        return new StrictUnifiedDiffOutputBuilder([
+            'addLineNumbers' => false,
+            'contextLines' => 10000,
+            'header' => '',
+        ]);
     }
 }