diff --git a/lib/Cake/Cache/Cache.php b/lib/Cake/Cache/Cache.php
index 938df43189e..c6f54759c7b 100644
--- a/lib/Cake/Cache/Cache.php
+++ b/lib/Cake/Cache/Cache.php
@@ -156,11 +156,12 @@ protected static function _buildEngine($name) {
 		if (!is_subclass_of($cacheClass, 'Cake\Cache\CacheEngine')) {
 			throw new Error\CacheException(__d('cake_dev', 'Cache engines must use Cake\Cache\CacheEngine as a base class.'));
 		}
-		static::$_engines[$name] = new $cacheClass();
-		if (static::$_engines[$name]->init($config)) {
-			if (static::$_engines[$name]->settings['probability'] && time() % static::$_engines[$name]->settings['probability'] === 0) {
-				static::$_engines[$name]->gc();
+		$engine = new $cacheClass();
+		if ($engine->init($config)) {
+			if ($engine->settings['probability'] && time() % $engine->settings['probability'] === 0) {
+				$engine->gc();
 			}
+			static::$_engines[$name] = $engine;
 			return true;
 		}
 		return false;
@@ -204,16 +205,18 @@ public static function drop($config) {
  * triggered.
  *
  * @param string $config The configuration name you want an engine.
+ * @param Cake\Cache\CacheEngine $engine An engine instance if you are manually
+ *   injecting a cache engine.
  * @return Cake\Cache\Engine
  */
-	public static function engine($config) {
+	public static function engine($config, CacheEngine $engine = null) {
 		if (Configure::read('Cache.disable')) {
 			return false;
 		}
 		if (isset(static::$_engines[$config])) {
 			return static::$_engines[$config];
 		}
-		if (!static::_buildEngine($config)) {
+		if (!$engine && !static::_buildEngine($config, $engine)) {
 			$message = __d(
 				'cake_dev',
 				'The "%s" cache configuration does not exist, nor could configuration be found at "Cache.%s".',
@@ -222,6 +225,9 @@ public static function engine($config) {
 			);
 			trigger_error($message, E_USER_WARNING);
 		}
+		if ($engine) {
+			static::$_engines[$config] = $engine;
+		}
 		return static::$_engines[$config];
 	}
 
diff --git a/lib/Cake/Test/TestCase/Cache/CacheTest.php b/lib/Cake/Test/TestCase/Cache/CacheTest.php
index e979fb255d8..43ae9da8990 100644
--- a/lib/Cake/Test/TestCase/Cache/CacheTest.php
+++ b/lib/Cake/Test/TestCase/Cache/CacheTest.php
@@ -154,11 +154,22 @@ public function testDecrementNonExistingConfig() {
 	public function testAttemptingToConfigureANonCacheEngineClass() {
 		$this->getMock('\StdClass', array(), array(), 'RubbishEngine');
 		Configure::write('Cache.wrong', array(
-			'engine' => __NAMESPACE__ . '\Rubbish'
+			'engine' => '\RubbishEngine'
 		));
 		Cache::engine('wrong');
 	}
 
+/**
+ * Test that engine() can be used to inject instances.
+ *
+ * @return void
+ */
+	public function testSetEngineValid() {
+		$engine = $this->getMockForAbstractClass('\Cake\Cache\CacheEngine');
+		Cache::engine('test', $engine);
+		$this->assertSame($engine, Cache::engine('test'));
+	}
+
 /**
  * test that calling config() sets the 'default' configuration up.
  *