diff --git a/src/Symfony/Component/Cache/Adapter/AbstractAdapter.php b/src/Symfony/Component/Cache/Adapter/AbstractAdapter.php
index a1f0de7dcaefd..f086064a33914 100644
--- a/src/Symfony/Component/Cache/Adapter/AbstractAdapter.php
+++ b/src/Symfony/Component/Cache/Adapter/AbstractAdapter.php
@@ -16,6 +16,7 @@
 use Psr\Log\LoggerAwareTrait;
 use Psr\Log\LoggerInterface;
 use Symfony\Component\Cache\CacheItem;
+use Symfony\Component\Cache\Exception\InvalidArgumentException;
 
 /**
  * @author Nicolas Grekas <p@tchwork.com>
@@ -32,9 +33,17 @@ abstract class AbstractAdapter implements AdapterInterface, LoggerAwareInterface
     private $createCacheItem;
     private $mergeByLifetime;
 
+    /**
+     * @var int|null The maximum length to enforce for identifiers or null when no limit applies
+     */
+    protected $maxIdLength;
+
     protected function __construct($namespace = '', $defaultLifetime = 0)
     {
-        $this->namespace = '' === $namespace ? '' : $this->getId($namespace);
+        $this->namespace = '' === $namespace ? '' : $this->getId($namespace).':';
+        if (null !== $this->maxIdLength && strlen($namespace) > $this->maxIdLength - 24) {
+            throw new InvalidArgumentException(sprintf('Namespace must be %d chars max, %d given ("%s")', $this->maxIdLength - 24, strlen($namespace), $namespace));
+        }
         $this->createCacheItem = \Closure::bind(
             function ($key, $value, $isHit) use ($defaultLifetime) {
                 $item = new CacheItem();
@@ -401,7 +410,14 @@ private function getId($key)
     {
         CacheItem::validateKey($key);
 
-        return $this->namespace.$key;
+        if (null === $this->maxIdLength) {
+            return $this->namespace.$key;
+        }
+        if (strlen($id = $this->namespace.$key) > $this->maxIdLength) {
+            $id = $this->namespace.substr_replace(base64_encode(md5($key, true)), ':', -2);
+        }
+
+        return $id;
     }
 
     private function generateItems($items, &$keys)
diff --git a/src/Symfony/Component/Cache/Adapter/ApcuAdapter.php b/src/Symfony/Component/Cache/Adapter/ApcuAdapter.php
index d0af11395700d..67afd5c72a89e 100644
--- a/src/Symfony/Component/Cache/Adapter/ApcuAdapter.php
+++ b/src/Symfony/Component/Cache/Adapter/ApcuAdapter.php
@@ -37,9 +37,9 @@ public function __construct($namespace = '', $defaultLifetime = 0, $version = nu
         if (null !== $version) {
             CacheItem::validateKey($version);
 
-            if (!apcu_exists($version.':'.$namespace)) {
+            if (!apcu_exists($version.'@'.$namespace)) {
                 $this->clear($namespace);
-                apcu_add($version.':'.$namespace, null);
+                apcu_add($version.'@'.$namespace, null);
             }
         }
     }
diff --git a/src/Symfony/Component/Cache/Tests/Adapter/MaxIdLengthAdapterTest.php b/src/Symfony/Component/Cache/Tests/Adapter/MaxIdLengthAdapterTest.php
new file mode 100644
index 0000000000000..8c96e7f969a7c
--- /dev/null
+++ b/src/Symfony/Component/Cache/Tests/Adapter/MaxIdLengthAdapterTest.php
@@ -0,0 +1,56 @@
+<?php
+
+/*
+ * This file is part of the Symfony package.
+ *
+ * (c) Fabien Potencier <fabien@symfony.com>
+ *
+ * For the full copyright and license information, please view the LICENSE
+ * file that was distributed with this source code.
+ */
+
+namespace Symfony\Component\Cache\Tests\Adapter;
+
+use Symfony\Component\Cache\Adapter\AbstractAdapter;
+
+class MaxIdLengthAdapterTest extends \PHPUnit_Framework_TestCase
+{
+    public function testLongKey()
+    {
+        $cache = $this->getMockBuilder(MaxIdLengthAdapter::class)
+            ->setConstructorArgs(array(str_repeat('-', 10)))
+            ->setMethods(array('doHave', 'doFetch', 'doDelete', 'doSave', 'doClear'))
+            ->getMock();
+
+        $cache->expects($this->exactly(2))
+            ->method('doHave')
+            ->withConsecutive(
+                array($this->equalTo('----------:nWfzGiCgLczv3SSUzXL3kg:')),
+                array($this->equalTo('----------:---------------------------------------'))
+            );
+
+        $cache->hasItem(str_repeat('-', 40));
+        $cache->hasItem(str_repeat('-', 39));
+    }
+
+    /**
+     * @expectedException \Symfony\Component\Cache\Exception\InvalidArgumentException
+     * @expectedExceptionMessage Namespace must be 26 chars max, 40 given ("----------------------------------------")
+     */
+    public function testTooLongNamespace()
+    {
+        $cache = $this->getMockBuilder(MaxIdLengthAdapter::class)
+            ->setConstructorArgs(array(str_repeat('-', 40)))
+            ->getMock();
+    }
+}
+
+abstract class MaxIdLengthAdapter extends AbstractAdapter
+{
+    protected $maxIdLength = 50;
+
+    public function __construct($ns)
+    {
+        parent::__construct($ns);
+    }
+}