diff --git a/.github/workflows/e2e.yaml b/.github/workflows/e2e.yaml
index 7a32cfbdef1..5dd3f0159f3 100644
--- a/.github/workflows/e2e.yaml
+++ b/.github/workflows/e2e.yaml
@@ -28,6 +28,7 @@ jobs:
                     - 'e2e/applied-polyfill-php80'
                     - 'e2e/config-dist-fallback'
                     - 'e2e/config-file-priority'
+                    - 'e2e/custom-file-extensions'
                     - 'e2e/only-option'
                     - 'e2e/parallel-custom-config'
                     - 'e2e/parallel-unused-skips'
diff --git a/e2e/custom-file-extensions/.gitignore b/e2e/custom-file-extensions/.gitignore
new file mode 100644
index 00000000000..61ead86667c
--- /dev/null
+++ b/e2e/custom-file-extensions/.gitignore
@@ -0,0 +1 @@
+/vendor
diff --git a/e2e/custom-file-extensions/composer.json b/e2e/custom-file-extensions/composer.json
new file mode 100644
index 00000000000..8b5ca727be7
--- /dev/null
+++ b/e2e/custom-file-extensions/composer.json
@@ -0,0 +1,5 @@
+{
+    "require": {
+        "php": "^8.1"
+    }
+}
diff --git a/e2e/custom-file-extensions/expected-output.diff b/e2e/custom-file-extensions/expected-output.diff
new file mode 100644
index 00000000000..1d3e214b4a4
--- /dev/null
+++ b/e2e/custom-file-extensions/expected-output.diff
@@ -0,0 +1,22 @@
+1 file with changes
+===================
+
+1) src/ChildService.inc:4
+
+    ---------- begin diff ----------
+@@ Line 4 @@
+
+ class ChildService extends ParentService
+ {
+-    public function run($value)
++    public function run($value, $flag = false)
+     {
+     }
+ }
+    ----------- end diff -----------
+
+Applied rules:
+ * AddParamBasedOnParentClassMethodRector
+
+
+ [OK] 1 file would have been changed (dry-run) by Rector
diff --git a/e2e/custom-file-extensions/rector.php b/e2e/custom-file-extensions/rector.php
new file mode 100644
index 00000000000..5382146d0ac
--- /dev/null
+++ b/e2e/custom-file-extensions/rector.php
@@ -0,0 +1,11 @@
+<?php
+
+declare(strict_types=1);
+
+use Rector\Config\RectorConfig;
+use Rector\Php80\Rector\ClassMethod\AddParamBasedOnParentClassMethodRector;
+
+return RectorConfig::configure()
+    ->withPaths([__DIR__ . '/src'])
+    ->withFileExtensions(['php', 'inc'])
+    ->withRules([AddParamBasedOnParentClassMethodRector::class]);
diff --git a/e2e/custom-file-extensions/src/ChildService.inc b/e2e/custom-file-extensions/src/ChildService.inc
new file mode 100644
index 00000000000..b16860183a5
--- /dev/null
+++ b/e2e/custom-file-extensions/src/ChildService.inc
@@ -0,0 +1,10 @@
+<?php
+
+namespace App;
+
+class ChildService extends ParentService
+{
+    public function run($value)
+    {
+    }
+}
diff --git a/e2e/custom-file-extensions/src/ParentService.inc b/e2e/custom-file-extensions/src/ParentService.inc
new file mode 100644
index 00000000000..e488251e868
--- /dev/null
+++ b/e2e/custom-file-extensions/src/ParentService.inc
@@ -0,0 +1,10 @@
+<?php
+
+namespace App;
+
+class ParentService
+{
+    public function run($value, $flag = false)
+    {
+    }
+}
diff --git a/src/NodeTypeResolver/DependencyInjection/PHPStanServicesFactory.php b/src/NodeTypeResolver/DependencyInjection/PHPStanServicesFactory.php
index 8755e439efa..b5612cdd573 100644
--- a/src/NodeTypeResolver/DependencyInjection/PHPStanServicesFactory.php
+++ b/src/NodeTypeResolver/DependencyInjection/PHPStanServicesFactory.php
@@ -50,7 +50,11 @@ public function __construct()
             $this->container = $containerFactory->create(
                 SimpleParameterProvider::provideStringParameter(Option::CONTAINER_CACHE_DIRECTORY),
                 $additionalConfigFiles,
-                []
+                [],
+                // let PHPStan find classes in files with any configured extension, not only in *.php ones
+                additionalParameters: [
+                    'fileExtensions' => SimpleParameterProvider::provideArrayParameter(Option::FILE_EXTENSIONS),
+                ]
             );
         } catch (Throwable $throwable) {
             if ($throwable->getMessage() === "File 'phar://phpstan.phar/conf/bleedingEdge.neon' is missing or is not readable.") {