diff --git a/src/Symfony/Component/DomCrawler/Crawler.php b/src/Symfony/Component/DomCrawler/Crawler.php
index dfc2fdcff3..5d86115b21 100644
--- a/src/Symfony/Component/DomCrawler/Crawler.php
+++ b/src/Symfony/Component/DomCrawler/Crawler.php
@@ -58,7 +58,9 @@ class Crawler extends \SplObjectStorage
      * This method uses the appropriate specialized add*() method based
      * on the type of the argument.
      *
-     * @param null|\DOMNodeList|array|\DOMNode $node A node
+     * @param \DOMNodeList|\DOMNode|array|string|null $node A node
+     *
+     * @throws \InvalidArgumentException When node is not the expected type.
      *
      * @api
      */
@@ -66,12 +68,19 @@ class Crawler extends \SplObjectStorage
     {
         if ($node instanceof \DOMNodeList) {
             $this->addNodeList($node);
+        } elseif ($node instanceof \DOMNode) {
+            $this->addNode($node);
         } elseif (is_array($node)) {
             $this->addNodes($node);
         } elseif (is_string($node)) {
             $this->addContent($node);
-        } elseif (is_object($node)) {
-            $this->addNode($node);
+        } elseif ($node !== null) {
+            throw new \InvalidArgumentException(
+                sprintf(
+                    'Expecting node to be DOMNodeList|DOMNode|array|string|null, but got %s',
+                    (is_object($node)) ? get_class($node) : gettype($node)
+                )
+            );
         }
     }
 
diff --git a/src/Symfony/Component/DomCrawler/Tests/CrawlerTest.php b/src/Symfony/Component/DomCrawler/Tests/CrawlerTest.php
index 76badb66a5..8dcdce9d30 100644
--- a/src/Symfony/Component/DomCrawler/Tests/CrawlerTest.php
+++ b/src/Symfony/Component/DomCrawler/Tests/CrawlerTest.php
@@ -53,6 +53,15 @@ class CrawlerTest extends \PHPUnit_Framework_TestCase
         $this->assertEquals('Foo', $crawler->filterXPath('//body')->text(), '->add() adds nodes from a string');
     }
 
+    /**
+     * @expectedException \InvalidArgumentException
+     */
+    public function testAddInvalidNode()
+    {
+        $crawler = new Crawler();
+        $crawler->add(1);
+    }
+
     /**
      * @covers Symfony\Component\DomCrawler\Crawler::addHtmlContent
      */