diff --git a/src/Symfony/Component/CssSelector/Tokenizer.php b/src/Symfony/Component/CssSelector/Tokenizer.php
index 67d5b67470..34e8ac580a 100644
--- a/src/Symfony/Component/CssSelector/Tokenizer.php
+++ b/src/Symfony/Component/CssSelector/Tokenizer.php
@@ -129,7 +129,7 @@ class Tokenizer
             }
 
             $result = substr($s, $start, $next - $start);
-            if ('\\' === $result[strlen($result) - 1]) {
+            if (strlen($result) > 0 && '\\' === $result[strlen($result) - 1]) {
                 // next quote character is escaped
                 $pos = $next + 1;
                 continue;
diff --git a/tests/Symfony/Tests/Component/CssSelector/TokenizerTest.php b/tests/Symfony/Tests/Component/CssSelector/TokenizerTest.php
index 4e780831c2..70f471e197 100644
--- a/tests/Symfony/Tests/Component/CssSelector/TokenizerTest.php
+++ b/tests/Symfony/Tests/Component/CssSelector/TokenizerTest.php
@@ -34,6 +34,7 @@ class TokenizerTest extends \PHPUnit_Framework_TestCase
     {
         $this->assertEquals('foo[class=foo bar  ]', $this->tokensToString($this->tokenizer->tokenize('foo[class="foo bar"]')), '->tokenize() lexes an input string and returns an array of tokens');
         $this->assertEquals("foo[class=foo Abar     ]", $this->tokensToString($this->tokenizer->tokenize('foo[class="foo \\65 bar"]')), '->tokenize() lexes an input string and returns an array of tokens');
+        $this->assertEquals("img[alt=  ]", $this->tokensToString($this->tokenizer->tokenize('img[alt=""]')), '->tokenize() lexes an input string and returns an array of tokens');
     }
 
     /**