diff --git a/src/Symfony/Component/Config/Resource/ClassExistenceResource.php b/src/Symfony/Component/Config/Resource/ClassExistenceResource.php
index e7ab1b8d7288..1ba8e7624832 100644
--- a/src/Symfony/Component/Config/Resource/ClassExistenceResource.php
+++ b/src/Symfony/Component/Config/Resource/ClassExistenceResource.php
@@ -155,7 +155,7 @@ public static function throwOnRequiredClass($class, \Exception $previous = null)
             throw $previous;
         }
 
-        $e = new \ReflectionException("Class $class not found", 0, $previous);
+        $e = new \ReflectionException(sprintf('Class "%s" not found while loading "%s".', $class, self::$autoloadedClass), 0, $previous);
 
         if (null !== $previous) {
             throw $e;
diff --git a/src/Symfony/Component/Config/Tests/Resource/ClassExistenceResourceTest.php b/src/Symfony/Component/Config/Tests/Resource/ClassExistenceResourceTest.php
index ad331240deba..b7ae81eaa6dd 100644
--- a/src/Symfony/Component/Config/Tests/Resource/ClassExistenceResourceTest.php
+++ b/src/Symfony/Component/Config/Tests/Resource/ClassExistenceResourceTest.php
@@ -84,7 +84,7 @@ public function testBadParentWithTimestamp()
     public function testBadParentWithNoTimestamp()
     {
         $this->expectException('ReflectionException');
-        $this->expectExceptionMessage('Class Symfony\Component\Config\Tests\Fixtures\MissingParent not found');
+        $this->expectExceptionMessage('Class "Symfony\Component\Config\Tests\Fixtures\MissingParent" not found while loading "Symfony\Component\Config\Tests\Fixtures\BadParent".');
 
         $res = new ClassExistenceResource(BadParent::class, false);
         $res->isFresh(0);
diff --git a/src/Symfony/Component/DependencyInjection/ContainerBuilder.php b/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
index 53873c15e625..f9bfcb52109d 100644
--- a/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
+++ b/src/Symfony/Component/DependencyInjection/ContainerBuilder.php
@@ -361,7 +361,7 @@ public function getReflectionClass($class, $throw = true)
             return null;
         }
 
-        $resource = null;
+        $resource = $classReflector = null;
 
         try {
             if (isset($this->classReflectors[$class])) {
@@ -376,7 +376,6 @@ public function getReflectionClass($class, $throw = true)
             if ($throw) {
                 throw $e;
             }
-            $classReflector = false;
         }
 
         if ($this->trackResources) {
diff --git a/src/Symfony/Component/DependencyInjection/Loader/FileLoader.php b/src/Symfony/Component/DependencyInjection/Loader/FileLoader.php
index 186c9c4cec7c..77cad3c046d7 100644
--- a/src/Symfony/Component/DependencyInjection/Loader/FileLoader.php
+++ b/src/Symfony/Component/DependencyInjection/Loader/FileLoader.php
@@ -149,12 +149,7 @@ private function findClasses($namespace, $pattern, $excludePattern)
             try {
                 $r = $this->container->getReflectionClass($class);
             } catch (\ReflectionException $e) {
-                $classes[$class] = sprintf(
-                    'While discovering services from namespace "%s", an error was thrown when processing the class "%s": "%s".',
-                    $namespace,
-                    $class,
-                    $e->getMessage()
-                );
+                $classes[$class] = $e->getMessage();
                 continue;
             }
             // check to make sure the expected class exists
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Compiler/AutowirePassTest.php b/src/Symfony/Component/DependencyInjection/Tests/Compiler/AutowirePassTest.php
index 7eb7f6024696..c5bcc660a5e4 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Compiler/AutowirePassTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Compiler/AutowirePassTest.php
@@ -380,7 +380,7 @@ public function testClassNotFoundThrowsException()
     public function testParentClassNotFoundThrowsException()
     {
         $this->expectException('Symfony\Component\DependencyInjection\Exception\AutowiringFailedException');
-        $this->expectExceptionMessage('Cannot autowire service "a": argument "$r" of method "Symfony\Component\DependencyInjection\Tests\Compiler\BadParentTypeHintedArgument::__construct()" has type "Symfony\Component\DependencyInjection\Tests\Compiler\OptionalServiceClass" but this class is missing a parent class (Class Symfony\Bug\NotExistClass not found).');
+        $this->expectExceptionMessageRegExp('{^Cannot autowire service "a": argument "\$r" of method "(Symfony\\\\Component\\\\DependencyInjection\\\\Tests\\\\Compiler\\\\)BadParentTypeHintedArgument::__construct\(\)" has type "\1OptionalServiceClass" but this class is missing a parent class \(Class "?Symfony\\\\Bug\\\\NotExistClass"? not found}');
 
         $container = new ContainerBuilder();
 
diff --git a/src/Symfony/Component/DependencyInjection/Tests/Loader/FileLoaderTest.php b/src/Symfony/Component/DependencyInjection/Tests/Loader/FileLoaderTest.php
index b6a816e40898..ffe58a67ef3b 100644
--- a/src/Symfony/Component/DependencyInjection/Tests/Loader/FileLoaderTest.php
+++ b/src/Symfony/Component/DependencyInjection/Tests/Loader/FileLoaderTest.php
@@ -178,9 +178,9 @@ public function testMissingParentClass()
 
         $this->assertTrue($container->has(MissingParent::class));
 
-        $this->assertSame(
-            ['While discovering services from namespace "Symfony\Component\DependencyInjection\Tests\Fixtures\Prototype\BadClasses\", an error was thrown when processing the class "Symfony\Component\DependencyInjection\Tests\Fixtures\Prototype\BadClasses\MissingParent": "Class Symfony\Component\DependencyInjection\Tests\Fixtures\Prototype\BadClasses\MissingClass not found".'],
-            $container->getDefinition(MissingParent::class)->getErrors()
+        $this->assertRegExp(
+            '{Class "?Symfony\\\\Component\\\\DependencyInjection\\\\Tests\\\\Fixtures\\\\Prototype\\\\BadClasses\\\\MissingClass"? not found}',
+            $container->getDefinition(MissingParent::class)->getErrors()[0]
         );
     }