diff --git a/lib/Doctrine/ORM/Tools/Setup.php b/lib/Doctrine/ORM/Tools/Setup.php
index 666d627a4..2e8a8f915 100644
--- a/lib/Doctrine/ORM/Tools/Setup.php
+++ b/lib/Doctrine/ORM/Tools/Setup.php
@@ -123,31 +123,7 @@ class Setup
     {
         $proxyDir = $proxyDir ?: sys_get_temp_dir();
 
-        if ($isDevMode === false && $cache === null) {
-            if (extension_loaded('apc')) {
-                $cache = new \Doctrine\Common\Cache\ApcCache();
-            } elseif (ini_get('xcache.cacher')) {
-                $cache = new \Doctrine\Common\Cache\XcacheCache();
-            } elseif (extension_loaded('memcache')) {
-                $memcache = new \Memcache();
-                $memcache->connect('127.0.0.1');
-                $cache = new \Doctrine\Common\Cache\MemcacheCache();
-                $cache->setMemcache($memcache);
-            } elseif (extension_loaded('redis')) {
-                $redis = new \Redis();
-                $redis->connect('127.0.0.1');
-                $cache = new \Doctrine\Common\Cache\RedisCache();
-                $cache->setRedis($redis);
-            } else {
-                $cache = new ArrayCache();
-            }
-        } elseif ($cache === null) {
-            $cache = new ArrayCache();
-        }
-
-        if ($cache instanceof CacheProvider) {
-            $cache->setNamespace("dc2_" . md5($proxyDir) . "_"); // to avoid collisions
-        }
+        $cache = self::createCacheConfiguration($isDevMode, $proxyDir, $cache);
 
         $config = new Configuration();
         $config->setMetadataCacheImpl($cache);
@@ -159,4 +135,64 @@ class Setup
 
         return $config;
     }
+
+    private static function createCacheConfiguration(bool $isDevMode, string $proxyDir, ?Cache $cache) :  Cache
+    {
+        $cache = self::createCacheInstance($isDevMode, $cache);
+
+        if ( ! $cache instanceof CacheProvider) {
+            return $cache;
+        }
+
+        $namespace = $cache->getNamespace();
+
+        if ($namespace !== '') {
+            $namespace .= ':';
+        }
+
+        $cache->setNamespace($namespace . 'dc2_' . md5($proxyDir) . '_'); // to avoid collisions
+
+        return $cache;
+    }
+
+    private static function createCacheInstance(bool $isDevMode, ?Cache $cache) : Cache
+    {
+        if ($cache !== null) {
+            return $cache;
+        }
+
+        if ($isDevMode === true) {
+            return new ArrayCache();
+        }
+
+        if (extension_loaded('apc')) {
+            return new \Doctrine\Common\Cache\ApcCache();
+        }
+
+        if (ini_get('xcache.cacher')) {
+            return new \Doctrine\Common\Cache\XcacheCache();
+        }
+
+        if (extension_loaded('memcache')) {
+            $memcache = new \Memcache();
+            $memcache->connect('127.0.0.1');
+
+            $cache = new \Doctrine\Common\Cache\MemcacheCache();
+            $cache->setMemcache($memcache);
+
+            return $cache;
+        }
+
+        if (extension_loaded('redis')) {
+            $redis = new \Redis();
+            $redis->connect('127.0.0.1');
+
+            $cache = new \Doctrine\Common\Cache\RedisCache();
+            $cache->setRedis($redis);
+
+            return $cache;
+        }
+
+        return new ArrayCache();
+    }
 }
diff --git a/tests/Doctrine/Tests/ORM/Tools/SetupTest.php b/tests/Doctrine/Tests/ORM/Tools/SetupTest.php
index fc5bd6e71..c7ec7c6d1 100644
--- a/tests/Doctrine/Tests/ORM/Tools/SetupTest.php
+++ b/tests/Doctrine/Tests/ORM/Tools/SetupTest.php
@@ -76,6 +76,43 @@ class SetupTest extends OrmTestCase
         $this->assertInstanceOf(YamlDriver::class, $config->getMetadataDriverImpl());
     }
 
+    /**
+     * @group 5904
+     */
+    public function testCacheNamespaceShouldBeGeneratedWhenCacheIsNotGiven() : void
+    {
+        $config = Setup::createConfiguration(false, '/foo');
+        $cache  = $config->getMetadataCacheImpl();
+
+        self::assertSame('dc2_1effb2475fcfba4f9e8b8a1dbc8f3caf_', $cache->getNamespace());
+    }
+
+    /**
+     * @group 5904
+     */
+    public function testCacheNamespaceShouldBeGeneratedWhenCacheIsGivenButHasNoNamespace() : void
+    {
+        $config = Setup::createConfiguration(false, '/foo', new ArrayCache());
+        $cache  = $config->getMetadataCacheImpl();
+
+        self::assertSame('dc2_1effb2475fcfba4f9e8b8a1dbc8f3caf_', $cache->getNamespace());
+    }
+
+    /**
+     * @group 5904
+     */
+    public function testConfiguredCacheNamespaceShouldBeUsedAsPrefixOfGeneratedNamespace() : void
+    {
+        $originalCache = new ArrayCache();
+        $originalCache->setNamespace('foo');
+
+        $config = Setup::createConfiguration(false, '/foo', $originalCache);
+        $cache  = $config->getMetadataCacheImpl();
+
+        self::assertSame($originalCache, $cache);
+        self::assertSame('foo:dc2_1effb2475fcfba4f9e8b8a1dbc8f3caf_', $cache->getNamespace());
+    }
+
     /**
      * @group DDC-1350
      */