diff --git a/src/Symfony/Bridge/PhpUnit/.gitignore b/src/Symfony/Bridge/PhpUnit/.gitignore
index c49a5d8df5..9d8c4aadaf 100644
--- a/src/Symfony/Bridge/PhpUnit/.gitignore
+++ b/src/Symfony/Bridge/PhpUnit/.gitignore
@@ -1,3 +1,4 @@
 vendor/
 composer.lock
 phpunit.xml
+Tests/DeprecationErrorHandler/fake_vendor/symfony/error-handler/DebugClassLoader.php
diff --git a/src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler/Deprecation.php b/src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler/Deprecation.php
index 911d37495e..9eded1a14e 100644
--- a/src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler/Deprecation.php
+++ b/src/Symfony/Bridge/PhpUnit/DeprecationErrorHandler/Deprecation.php
@@ -13,6 +13,8 @@ namespace Symfony\Bridge\PhpUnit\DeprecationErrorHandler;
 
 use PHPUnit\Util\Test;
 use Symfony\Bridge\PhpUnit\Legacy\SymfonyTestsListenerFor;
+use Symfony\Component\Debug\DebugClassLoader as LegacyDebugClassLoader;
+use Symfony\Component\ErrorHandler\DebugClassLoader;
 
 /**
  * @internal
@@ -53,6 +55,18 @@ class Deprecation
     public function __construct($message, array $trace, $file)
     {
         $this->trace = $trace;
+
+        if ('trigger_error' === ($trace[1]['function'] ?? null)
+            && (DebugClassLoader::class === ($class = $trace[2]['class'] ?? null) || LegacyDebugClassLoader::class === $class)
+            && 'checkClass' === ($trace[2]['function'] ?? null)
+            && null !== ($extraFile = $trace[2]['args'][1] ?? null)
+            && '' !== $extraFile
+            && false !== $extraFile = realpath($extraFile)
+        ) {
+            $this->getOriginalFilesStack();
+            array_splice($this->originalFilesStack, 2, 1, $extraFile);
+        }
+
         $this->message = $message;
         $i = \count($trace);
         while (1 < $i && $this->lineShouldBeSkipped($trace[--$i])) {
diff --git a/src/Symfony/Bridge/PhpUnit/Tests/DeprecationErrorHandler/debug_class_loader_autoload.phpt b/src/Symfony/Bridge/PhpUnit/Tests/DeprecationErrorHandler/debug_class_loader_autoload.phpt
new file mode 100644
index 0000000000..781027e84f
--- /dev/null
+++ b/src/Symfony/Bridge/PhpUnit/Tests/DeprecationErrorHandler/debug_class_loader_autoload.phpt
@@ -0,0 +1,51 @@
+--TEST--
+Test that a deprecation from the DebugClassLoader on a vendor class autoload triggered by an app class is considered indirect.
+--FILE--
+<?php
+
+$k = 'SYMFONY_DEPRECATIONS_HELPER';
+putenv($k.'='.$_SERVER[$k] = $_ENV[$k] = 'max[total]=0');
+putenv('ANSICON');
+putenv('ConEmuANSI');
+putenv('TERM');
+
+$vendor = __DIR__;
+while (!file_exists($vendor.'/vendor')) {
+    $vendor = dirname($vendor);
+}
+define('PHPUNIT_COMPOSER_INSTALL', $vendor.'/vendor/autoload.php');
+require PHPUNIT_COMPOSER_INSTALL;
+require_once __DIR__.'/../../bootstrap.php';
+eval(<<<'EOPHP'
+namespace PHPUnit\Util;
+
+class Test
+{
+    public static function getGroups()
+    {
+        return array();
+    }
+}
+EOPHP
+);
+require __DIR__.'/fake_vendor/autoload.php';
+
+// We need the real DebugClassLoader FQCN but in a vendor path.
+if (!file_exists($errorHandlerRootDir = __DIR__.'/../../../../Component/ErrorHandler')) {
+    if (!file_exists($errorHandlerRootDir = __DIR__.'/../../vendor/symfony/error-handler')) {
+        die('Could not find the ErrorHandler component root directory.');
+    }
+}
+
+file_put_contents($fakeDebugClassLoadPath = __DIR__.'/fake_vendor/symfony/error-handler/DebugClassLoader.php', file_get_contents($errorHandlerRootDir.'/DebugClassLoader.php'));
+require $fakeDebugClassLoadPath;
+
+\Symfony\Component\ErrorHandler\DebugClassLoader::enable();
+new \App\Services\BarService();
+
+?>
+--EXPECTF--
+Remaining indirect deprecation notices (1)
+
+  1x: The "acme\lib\ExtendsDeprecatedClassFromOtherVendor" class extends "fcy\lib\DeprecatedClass" that is deprecated.
+    1x in BarService::__construct from App\Services
diff --git a/src/Symfony/Bridge/PhpUnit/Tests/DeprecationErrorHandler/fake_app/BarService.php b/src/Symfony/Bridge/PhpUnit/Tests/DeprecationErrorHandler/fake_app/BarService.php
new file mode 100644
index 0000000000..868de5bd44
--- /dev/null
+++ b/src/Symfony/Bridge/PhpUnit/Tests/DeprecationErrorHandler/fake_app/BarService.php
@@ -0,0 +1,13 @@
+<?php
+
+namespace App\Services;
+
+use acme\lib\ExtendsDeprecatedClassFromOtherVendor;
+
+final class BarService
+{
+    public function __construct()
+    {
+        ExtendsDeprecatedClassFromOtherVendor::FOO;
+    }
+}
diff --git a/src/Symfony/Bridge/PhpUnit/Tests/DeprecationErrorHandler/fake_vendor/acme/lib/ExtendsDeprecatedClassFromOtherVendor.php b/src/Symfony/Bridge/PhpUnit/Tests/DeprecationErrorHandler/fake_vendor/acme/lib/ExtendsDeprecatedClassFromOtherVendor.php
new file mode 100644
index 0000000000..f748109dba
--- /dev/null
+++ b/src/Symfony/Bridge/PhpUnit/Tests/DeprecationErrorHandler/fake_vendor/acme/lib/ExtendsDeprecatedClassFromOtherVendor.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace acme\lib;
+
+use fcy\lib\DeprecatedClass;
+
+final class ExtendsDeprecatedClassFromOtherVendor extends DeprecatedClass
+{
+    public const FOO = 'bar';
+}
diff --git a/src/Symfony/Bridge/PhpUnit/Tests/DeprecationErrorHandler/fake_vendor/composer/autoload_real.php b/src/Symfony/Bridge/PhpUnit/Tests/DeprecationErrorHandler/fake_vendor/composer/autoload_real.php
index 2446550e2a..f8221401c7 100644
--- a/src/Symfony/Bridge/PhpUnit/Tests/DeprecationErrorHandler/fake_vendor/composer/autoload_real.php
+++ b/src/Symfony/Bridge/PhpUnit/Tests/DeprecationErrorHandler/fake_vendor/composer/autoload_real.php
@@ -12,23 +12,33 @@ class ComposerLoaderFake
         return [
             'App\\Services\\' => [__DIR__.'/../../fake_app/'],
             'acme\\lib\\' => [__DIR__.'/../acme/lib/'],
+            'fcy\\lib\\' => [__DIR__.'/../fcy/lib/'],
         ];
     }
 
     public function loadClass($className)
+    {
+        if ($file = $this->findFile($className)) {
+            require $file;
+        }
+    }
+
+    public function findFile($class)
     {
         foreach ($this->getPrefixesPsr4() as $prefix => $baseDirs) {
-            if (strpos($className, $prefix) !== 0) {
+            if (strpos($class, $prefix) !== 0) {
                 continue;
             }
 
             foreach ($baseDirs as $baseDir) {
-                $file = str_replace([$prefix, '\\'], [$baseDir, '/'], $className.'.php');
+                $file = str_replace([$prefix, '\\'], [$baseDir, '/'], $class.'.php');
                 if (file_exists($file)) {
-                    require $file;
+                    return $file;
                 }
             }
         }
+
+        return false;
     }
 }
 
diff --git a/src/Symfony/Bridge/PhpUnit/Tests/DeprecationErrorHandler/fake_vendor/fcy/lib/DeprecatedClass.php b/src/Symfony/Bridge/PhpUnit/Tests/DeprecationErrorHandler/fake_vendor/fcy/lib/DeprecatedClass.php
new file mode 100644
index 0000000000..f6672cea20
--- /dev/null
+++ b/src/Symfony/Bridge/PhpUnit/Tests/DeprecationErrorHandler/fake_vendor/fcy/lib/DeprecatedClass.php
@@ -0,0 +1,10 @@
+<?php
+
+namespace fcy\lib;
+
+/**
+ * @deprecated
+ */
+class DeprecatedClass
+{
+}
diff --git a/src/Symfony/Bridge/PhpUnit/Tests/DeprecationErrorHandler/fake_vendor/symfony/error-handler/.gitkeep b/src/Symfony/Bridge/PhpUnit/Tests/DeprecationErrorHandler/fake_vendor/symfony/error-handler/.gitkeep
new file mode 100644
index 0000000000..e69de29bb2
diff --git a/src/Symfony/Bridge/PhpUnit/composer.json b/src/Symfony/Bridge/PhpUnit/composer.json
index 85318fe178..24ec52101a 100644
--- a/src/Symfony/Bridge/PhpUnit/composer.json
+++ b/src/Symfony/Bridge/PhpUnit/composer.json
@@ -20,6 +20,9 @@
         "php": "THIS BRIDGE WHEN TESTING LOWEST SYMFONY VERSIONS.",
         "php": ">=5.5.9"
     },
+    "require-dev": {
+        "symfony/error-handler": "^4.4|^5.0"
+    },
     "suggest": {
         "symfony/error-handler": "For tracking deprecated interfaces usages at runtime with DebugClassLoader"
     },