diff --git a/src/Symfony/Component/HttpFoundation/Response.php b/src/Symfony/Component/HttpFoundation/Response.php
index 9844775ee2..d4b8b2718a 100644
--- a/src/Symfony/Component/HttpFoundation/Response.php
+++ b/src/Symfony/Component/HttpFoundation/Response.php
@@ -171,7 +171,7 @@ class Response
         428 => 'Precondition Required',                                       // RFC6585
         429 => 'Too Many Requests',                                           // RFC6585
         431 => 'Request Header Fields Too Large',                             // RFC6585
-        451 => 'Unavailable For Legal Reasons',
+        451 => 'Unavailable For Legal Reasons',                               // RFC7725
         500 => 'Internal Server Error',
         501 => 'Not Implemented',
         502 => 'Bad Gateway',
diff --git a/src/Symfony/Component/Yaml/Dumper.php b/src/Symfony/Component/Yaml/Dumper.php
index 39cdcfc536..21351a5c34 100644
--- a/src/Symfony/Component/Yaml/Dumper.php
+++ b/src/Symfony/Component/Yaml/Dumper.php
@@ -32,6 +32,10 @@ class Dumper
      */
     public function setIndentation($num)
     {
+        if ($num < 1) {
+            throw new \InvalidArgumentException('The indentation must be greater than zero.');
+        }
+
         $this->indentation = (int) $num;
     }
 
diff --git a/src/Symfony/Component/Yaml/Tests/DumperTest.php b/src/Symfony/Component/Yaml/Tests/DumperTest.php
index 2a0df692b3..84069d8aef 100644
--- a/src/Symfony/Component/Yaml/Tests/DumperTest.php
+++ b/src/Symfony/Component/Yaml/Tests/DumperTest.php
@@ -228,6 +228,24 @@ EOF;
             'paragraph-separator' => array("\t\\P", '"\t\\\\P"'),
         );
     }
+
+    /**
+     * @expectedException \InvalidArgumentException
+     * @expectedExceptionMessage The indentation must be greater than zero
+     */
+    public function testZeroIndentationThrowsException()
+    {
+        $this->dumper->setIndentation(0);
+    }
+
+    /**
+     * @expectedException \InvalidArgumentException
+     * @expectedExceptionMessage The indentation must be greater than zero
+     */
+    public function testNegativeIndentationThrowsException()
+    {
+        $this->dumper->setIndentation(-4);
+    }
 }
 
 class A
diff --git a/src/Symfony/Component/Yaml/Tests/YamlTest.php b/src/Symfony/Component/Yaml/Tests/YamlTest.php
index 8db65e3990..883ee835a0 100644
--- a/src/Symfony/Component/Yaml/Tests/YamlTest.php
+++ b/src/Symfony/Component/Yaml/Tests/YamlTest.php
@@ -34,4 +34,22 @@ class YamlTest extends \PHPUnit_Framework_TestCase
         $parsedByContents = Yaml::parse($contents);
         $this->assertEquals($parsedByFilename, $parsedByContents);
     }
+
+    /**
+     * @expectedException \InvalidArgumentException
+     * @expectedExceptionMessage The indentation must be greater than zero
+     */
+    public function testZeroIndentationThrowsException()
+    {
+        Yaml::dump(array('lorem' => 'ipsum', 'dolor' => 'sit'), 2, 0);
+    }
+
+    /**
+     * @expectedException \InvalidArgumentException
+     * @expectedExceptionMessage The indentation must be greater than zero
+     */
+    public function testNegativeIndentationThrowsException()
+    {
+        Yaml::dump(array('lorem' => 'ipsum', 'dolor' => 'sit'), 2, -4);
+    }
 }
diff --git a/src/Symfony/Component/Yaml/Yaml.php b/src/Symfony/Component/Yaml/Yaml.php
index be05a36533..374365492f 100644
--- a/src/Symfony/Component/Yaml/Yaml.php
+++ b/src/Symfony/Component/Yaml/Yaml.php
@@ -88,6 +88,10 @@ class Yaml
      */
     public static function dump($array, $inline = 2, $indent = 4, $exceptionOnInvalidType = false, $objectSupport = false)
     {
+        if ($indent < 1) {
+            throw new \InvalidArgumentException('The indentation must be greater than zero.');
+        }
+
         $yaml = new Dumper();
         $yaml->setIndentation($indent);