diff --git a/src/Symfony/Component/Config/Resource/ClassExistenceResource.php b/src/Symfony/Component/Config/Resource/ClassExistenceResource.php
index 4e0d0d834e..685da72850 100644
--- a/src/Symfony/Component/Config/Resource/ClassExistenceResource.php
+++ b/src/Symfony/Component/Config/Resource/ClassExistenceResource.php
@@ -36,7 +36,7 @@ class ClassExistenceResource implements SelfCheckingResourceInterface, \Serializ
     {
         $this->resource = $resource;
         if (null !== $exists) {
-            $this->exists = (bool) $exists;
+            $this->exists = [(bool) $exists, null];
         }
     }
 
@@ -65,9 +65,13 @@ class ClassExistenceResource implements SelfCheckingResourceInterface, \Serializ
     {
         $loaded = class_exists($this->resource, false) || interface_exists($this->resource, false) || trait_exists($this->resource, false);
 
-        if (null !== $exists = &self::$existsCache[(int) (0 >= $timestamp)][$this->resource]) {
-            $exists = $exists || $loaded;
-        } elseif (!$exists = $loaded) {
+        if (null !== $exists = &self::$existsCache[$this->resource]) {
+            if ($loaded) {
+                $exists = [true, null];
+            } elseif (0 >= $timestamp && !$exists[0] && null !== $exists[1]) {
+                throw new \ReflectionException($exists[1]);
+            }
+        } elseif ([false, null] === $exists = [$loaded, null]) {
             if (!self::$autoloadLevel++) {
                 spl_autoload_register(__CLASS__.'::throwOnRequiredClass');
             }
@@ -75,16 +79,19 @@ class ClassExistenceResource implements SelfCheckingResourceInterface, \Serializ
             self::$autoloadedClass = ltrim($this->resource, '\\');
 
             try {
-                $exists = class_exists($this->resource) || interface_exists($this->resource, false) || trait_exists($this->resource, false);
+                $exists[0] = class_exists($this->resource) || interface_exists($this->resource, false) || trait_exists($this->resource, false);
             } catch (\Exception $e) {
+                $exists[1] = $e->getMessage();
+
                 try {
                     self::throwOnRequiredClass($this->resource, $e);
                 } catch (\ReflectionException $e) {
                     if (0 >= $timestamp) {
-                        unset(self::$existsCache[1][$this->resource]);
                         throw $e;
                     }
                 }
+            } catch (\Throwable $e) {
+                $exists[1] = $e->getMessage();
             } finally {
                 self::$autoloadedClass = $autoloadedClass;
                 if (!--self::$autoloadLevel) {
@@ -97,7 +104,7 @@ class ClassExistenceResource implements SelfCheckingResourceInterface, \Serializ
             $this->exists = $exists;
         }
 
-        return $this->exists xor !$exists;
+        return $this->exists[0] xor !$exists[0];
     }
 
     /**
@@ -118,6 +125,10 @@ class ClassExistenceResource implements SelfCheckingResourceInterface, \Serializ
     public function unserialize($serialized)
     {
         list($this->resource, $this->exists) = unserialize($serialized);
+
+        if (\is_bool($this->exists)) {
+            $this->exists = [$this->exists, null];
+        }
     }
 
     /**
@@ -155,7 +166,17 @@ class ClassExistenceResource implements SelfCheckingResourceInterface, \Serializ
             throw $previous;
         }
 
-        $e = new \ReflectionException(sprintf('Class "%s" not found while loading "%s".', $class, self::$autoloadedClass), 0, $previous);
+        $message = sprintf('Class "%s" not found.', $class);
+
+        if (self::$autoloadedClass !== $class) {
+            $message = substr_replace($message, sprintf(' while loading "%s"', self::$autoloadedClass), -1, 0);
+        }
+
+        if (null !== $previous) {
+            $message = $previous->getMessage();
+        }
+
+        $e = new \ReflectionException($message, 0, $previous);
 
         if (null !== $previous) {
             throw $e;
diff --git a/src/Symfony/Component/Config/Tests/Fixtures/BadFileName.php b/src/Symfony/Component/Config/Tests/Fixtures/BadFileName.php
new file mode 100644
index 0000000000..0f79bdd523
--- /dev/null
+++ b/src/Symfony/Component/Config/Tests/Fixtures/BadFileName.php
@@ -0,0 +1,9 @@
+<?php
+
+namespace Symfony\Component\Config\Tests\Fixtures;
+
+class FileNameMismatchOnPurpose
+{
+}
+
+throw new \RuntimeException('Mismatch between file name and class name.');
diff --git a/src/Symfony/Component/Config/Tests/Resource/ClassExistenceResourceTest.php b/src/Symfony/Component/Config/Tests/Resource/ClassExistenceResourceTest.php
index b7ae81eaa6..07ed296dd6 100644
--- a/src/Symfony/Component/Config/Tests/Resource/ClassExistenceResourceTest.php
+++ b/src/Symfony/Component/Config/Tests/Resource/ClassExistenceResourceTest.php
@@ -13,6 +13,7 @@ namespace Symfony\Component\Config\Tests\Resource;
 
 use PHPUnit\Framework\TestCase;
 use Symfony\Component\Config\Resource\ClassExistenceResource;
+use Symfony\Component\Config\Tests\Fixtures\BadFileName;
 use Symfony\Component\Config\Tests\Fixtures\BadParent;
 use Symfony\Component\Config\Tests\Fixtures\Resource\ConditionalClass;
 
@@ -90,6 +91,24 @@ EOF
         $res->isFresh(0);
     }
 
+    public function testBadFileName()
+    {
+        $this->expectException('ReflectionException');
+        $this->expectExceptionMessage('Mismatch between file name and class name.');
+
+        $res = new ClassExistenceResource(BadFileName::class, false);
+        $res->isFresh(0);
+    }
+
+    public function testBadFileNameBis()
+    {
+        $this->expectException('ReflectionException');
+        $this->expectExceptionMessage('Mismatch between file name and class name.');
+
+        $res = new ClassExistenceResource(BadFileName::class, false);
+        $res->isFresh(0);
+    }
+
     public function testConditionalClass()
     {
         $res = new ClassExistenceResource(ConditionalClass::class, false);