diff --git a/src/Symfony/Component/HttpFoundation/IpUtils.php b/src/Symfony/Component/HttpFoundation/IpUtils.php
index 82461d0159..28093be434 100644
--- a/src/Symfony/Component/HttpFoundation/IpUtils.php
+++ b/src/Symfony/Component/HttpFoundation/IpUtils.php
@@ -61,11 +61,14 @@ class IpUtils
      */
     public static function checkIp4($requestIp, $ip)
     {
+        if (!filter_var($requestIp, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4)) {
+            return false;
+        }
+
         if (false !== strpos($ip, '/')) {
             list($address, $netmask) = explode('/', $ip, 2);
 
             if ($netmask === '0') {
-                // Ensure IP is valid - using ip2long below implicitly validates, but we need to do it manually here
                 return filter_var($address, FILTER_VALIDATE_IP, FILTER_FLAG_IPV4);
             }
 
diff --git a/src/Symfony/Component/HttpFoundation/Tests/IpUtilsTest.php b/src/Symfony/Component/HttpFoundation/Tests/IpUtilsTest.php
index 877053f0f3..a6d28a2943 100644
--- a/src/Symfony/Component/HttpFoundation/Tests/IpUtilsTest.php
+++ b/src/Symfony/Component/HttpFoundation/Tests/IpUtilsTest.php
@@ -37,6 +37,7 @@ class IpUtilsTest extends \PHPUnit_Framework_TestCase
             array(true, '1.2.3.4', '0.0.0.0/0'),
             array(true, '1.2.3.4', '192.168.1.0/0'),
             array(false, '1.2.3.4', '256.256.256/0'), // invalid CIDR notation
+            array(false, 'an_invalid_ip', '192.168.1.0/24'),
         );
     }