diff --git a/src/Fixable/Patcher.php b/src/Fixable/Patcher.php
index dcacfec92a..7f126361a4 100644
--- a/src/Fixable/Patcher.php
+++ b/src/Fixable/Patcher.php
@@ -19,6 +19,7 @@
 use function sha1;
 use function str_starts_with;
 use function substr;
+use const PHP_VERSION_ID;
 use const PREG_SPLIT_DELIM_CAPTURE;
 use const PREG_SPLIT_NO_EMPTY;
 
@@ -62,7 +63,9 @@ public function applyDiffs(string $fileName, array $diffs): string
 
 		$refMerge = new ReflectionClass(PhpMerge::class);
 		$refMergeMethod = $refMerge->getMethod('mergeHunks');
-		$refMergeMethod->setAccessible(true);
+		if (PHP_VERSION_ID < 80100) {
+			$refMergeMethod->setAccessible(true);
+		}
 
 		$result = Line::createArray(array_map(
 			static fn ($l) => [$l, Differ::OLD],
diff --git a/src/Testing/TestCaseSourceLocatorFactory.php b/src/Testing/TestCaseSourceLocatorFactory.php
index a87bf4d9df..9cddb78e99 100644
--- a/src/Testing/TestCaseSourceLocatorFactory.php
+++ b/src/Testing/TestCaseSourceLocatorFactory.php
@@ -68,7 +68,9 @@ public function create(): SourceLocator
 				),
 			];
 			$vendorDirProperty = $classLoaderReflection->getProperty('vendorDir');
-			$vendorDirProperty->setAccessible(true);
+			if (PHP_VERSION_ID < 80100) {
+				$vendorDirProperty->setAccessible(true);
+			}
 			foreach ($classLoaders as $classLoader) {
 				$composerProjectPath = dirname($vendorDirProperty->getValue($classLoader));
 				if (!is_file($composerProjectPath . '/composer.json')) {