diff --git a/src/Symfony/Component/Validator/Constraints/FileValidator.php b/src/Symfony/Component/Validator/Constraints/FileValidator.php
index 52e937944188b..133b085ad4297 100644
--- a/src/Symfony/Component/Validator/Constraints/FileValidator.php
+++ b/src/Symfony/Component/Validator/Constraints/FileValidator.php
@@ -13,8 +13,10 @@
 
 use Symfony\Component\HttpFoundation\File\File as FileObject;
 use Symfony\Component\HttpFoundation\File\UploadedFile;
+use Symfony\Component\Mime\MimeTypes;
 use Symfony\Component\Validator\Constraint;
 use Symfony\Component\Validator\ConstraintValidator;
+use Symfony\Component\Validator\Exception\LogicException;
 use Symfony\Component\Validator\Exception\UnexpectedTypeException;
 use Symfony\Component\Validator\Exception\UnexpectedValueException;
 
@@ -170,12 +172,18 @@ public function validate($value, Constraint $constraint)
         }
 
         if ($constraint->mimeTypes) {
-            if (!$value instanceof FileObject) {
+            if (class_exists(MimeTypes::class)) {
+                $mime = MimeTypes::getDefault()->guessMimeType($path);
+            } else {
+                if (!class_exists(FileObject::class)) {
+                    throw new LogicException('You cannot validate the mime-type of files as the Mime component is not installed. Try running "composer require symfony/mime".');
+                }
+
                 $value = new FileObject($value);
+                $mime = $value->getMimeType();
             }
 
             $mimeTypes = (array) $constraint->mimeTypes;
-            $mime = $value->getMimeType();
 
             foreach ($mimeTypes as $mimeType) {
                 if ($mimeType === $mime) {
diff --git a/src/Symfony/Component/Validator/Tests/Constraints/FileValidatorTest.php b/src/Symfony/Component/Validator/Tests/Constraints/FileValidatorTest.php
index 0bbac3c6b70a9..6e024431d4153 100644
--- a/src/Symfony/Component/Validator/Tests/Constraints/FileValidatorTest.php
+++ b/src/Symfony/Component/Validator/Tests/Constraints/FileValidatorTest.php
@@ -11,6 +11,7 @@
 
 namespace Symfony\Component\Validator\Tests\Constraints;
 
+use Symfony\Component\HttpFoundation\File\File as FileObject;
 use Symfony\Component\HttpFoundation\File\UploadedFile;
 use Symfony\Component\Validator\Constraints\File;
 use Symfony\Component\Validator\Constraints\FileValidator;
@@ -283,21 +284,10 @@ public function testBinaryFormat($bytesWritten, $limit, $binaryFormat, $sizeAsSt
 
     public function testValidMimeType()
     {
-        $file = $this
-            ->getMockBuilder('Symfony\Component\HttpFoundation\File\File')
-            ->setConstructorArgs([__DIR__.'/Fixtures/foo'])
-            ->getMock();
-        $file
-            ->expects($this->once())
-            ->method('getPathname')
-            ->willReturn($this->path);
-        $file
-            ->expects($this->once())
-            ->method('getMimeType')
-            ->willReturn('image/jpg');
+        $file = new FileObject(__DIR__.'/Fixtures/blank.jpg');
 
         $constraint = new File([
-            'mimeTypes' => ['image/png', 'image/jpg'],
+            'mimeTypes' => ['image/png', 'image/jpeg'],
         ]);
 
         $this->validator->validate($file, $constraint);
@@ -307,18 +297,7 @@ public function testValidMimeType()
 
     public function testValidWildcardMimeType()
     {
-        $file = $this
-            ->getMockBuilder('Symfony\Component\HttpFoundation\File\File')
-            ->setConstructorArgs([__DIR__.'/Fixtures/foo'])
-            ->getMock();
-        $file
-            ->expects($this->once())
-            ->method('getPathname')
-            ->willReturn($this->path);
-        $file
-            ->expects($this->once())
-            ->method('getMimeType')
-            ->willReturn('image/jpg');
+        $file = new FileObject(__DIR__.'/Fixtures/test.gif');
 
         $constraint = new File([
             'mimeTypes' => ['image/*'],
@@ -331,21 +310,10 @@ public function testValidWildcardMimeType()
 
     public function testInvalidMimeType()
     {
-        $file = $this
-            ->getMockBuilder('Symfony\Component\HttpFoundation\File\File')
-            ->setConstructorArgs([__DIR__.'/Fixtures/foo'])
-            ->getMock();
-        $file
-            ->expects($this->once())
-            ->method('getPathname')
-            ->willReturn($this->path);
-        $file
-            ->expects($this->once())
-            ->method('getMimeType')
-            ->willReturn('application/pdf');
+        $file = new FileObject(__DIR__.'/Fixtures/blank.pdf');
 
         $constraint = new File([
-            'mimeTypes' => ['image/png', 'image/jpg'],
+            'mimeTypes' => ['image/png', 'image/jpeg'],
             'mimeTypesMessage' => 'myMessage',
         ]);
 
@@ -353,30 +321,19 @@ public function testInvalidMimeType()
 
         $this->buildViolation('myMessage')
             ->setParameter('{{ type }}', '"application/pdf"')
-            ->setParameter('{{ types }}', '"image/png", "image/jpg"')
-            ->setParameter('{{ file }}', '"'.$this->path.'"')
-            ->setParameter('{{ name }}', '"'.basename($this->path).'"')
+            ->setParameter('{{ types }}', '"image/png", "image/jpeg"')
+            ->setParameter('{{ file }}', '"'.__DIR__.'/Fixtures/blank.pdf'.'"')
+            ->setParameter('{{ name }}', '"blank.pdf"')
             ->setCode(File::INVALID_MIME_TYPE_ERROR)
             ->assertRaised();
     }
 
     public function testInvalidWildcardMimeType()
     {
-        $file = $this
-            ->getMockBuilder('Symfony\Component\HttpFoundation\File\File')
-            ->setConstructorArgs([__DIR__.'/Fixtures/foo'])
-            ->getMock();
-        $file
-            ->expects($this->once())
-            ->method('getPathname')
-            ->willReturn($this->path);
-        $file
-            ->expects($this->once())
-            ->method('getMimeType')
-            ->willReturn('application/pdf');
+        $file = new FileObject(__DIR__.'/Fixtures/blank.pdf');
 
         $constraint = new File([
-            'mimeTypes' => ['image/*', 'image/jpg'],
+            'mimeTypes' => ['image/*', 'image/jpeg'],
             'mimeTypesMessage' => 'myMessage',
         ]);
 
@@ -384,9 +341,9 @@ public function testInvalidWildcardMimeType()
 
         $this->buildViolation('myMessage')
             ->setParameter('{{ type }}', '"application/pdf"')
-            ->setParameter('{{ types }}', '"image/*", "image/jpg"')
-            ->setParameter('{{ file }}', '"'.$this->path.'"')
-            ->setParameter('{{ name }}', '"'.basename($this->path).'"')
+            ->setParameter('{{ types }}', '"image/*", "image/jpeg"')
+            ->setParameter('{{ file }}', '"'.__DIR__.'/Fixtures/blank.pdf'.'"')
+            ->setParameter('{{ name }}', '"blank.pdf"')
             ->setCode(File::INVALID_MIME_TYPE_ERROR)
             ->assertRaised();
     }
diff --git a/src/Symfony/Component/Validator/Tests/Constraints/Fixtures/blank.jpg b/src/Symfony/Component/Validator/Tests/Constraints/Fixtures/blank.jpg
new file mode 100644
index 0000000000000..51246b40a1265
Binary files /dev/null and b/src/Symfony/Component/Validator/Tests/Constraints/Fixtures/blank.jpg differ
diff --git a/src/Symfony/Component/Validator/Tests/Constraints/Fixtures/blank.pdf b/src/Symfony/Component/Validator/Tests/Constraints/Fixtures/blank.pdf
new file mode 100644
index 0000000000000..757bb1f36404f
Binary files /dev/null and b/src/Symfony/Component/Validator/Tests/Constraints/Fixtures/blank.pdf differ