diff --git a/framework/caching/Cache.php b/framework/caching/Cache.php
index 70cf8cb..fb56d5e 100644
--- a/framework/caching/Cache.php
+++ b/framework/caching/Cache.php
@@ -71,6 +71,18 @@ abstract class Cache extends Component implements \ArrayAccess
 
 
 	/**
+	 * Initializes the application component.
+	 * This method overrides the parent implementation by setting default cache key prefix.
+	 */
+	public function init()
+	{
+		parent::init();
+		if ($this->keyPrefix === null) {
+			$this->keyPrefix = \Yii::$app->id;
+		}
+	}
+
+	/**
 	 * Builds a normalized cache key from a given key.
 	 *
 	 * The generated key contains letters and digits only, and its length is no more than 32.
diff --git a/framework/caching/RedisCache.php b/framework/caching/RedisCache.php
index 74432f4..5841d66 100644
--- a/framework/caching/RedisCache.php
+++ b/framework/caching/RedisCache.php
@@ -20,8 +20,8 @@ use yii\db\redis\Connection;
  * When the server needs authentication, you can set the [[password]] property to
  * authenticate with the server after connect.
  *
- * See [[Cache]] for common cache operations that RedisCache supports.
- * Different from the description in [[Cache]] RedisCache allows the expire parameter of
+ * See [[Cache]] manual for common cache operations that RedisCache supports.
+ * Different from the description in [[Cache]], RedisCache allows the expire parameter of
  * [[set]] and [[add]] to be a floating point number, so you may specify the time in milliseconds.
  *
  * To use RedisCache as the cache application component, configure the application as follows,
@@ -39,12 +39,6 @@ use yii\db\redis\Connection;
  * )
  * ~~~
  *
- * In the above, two memcache servers are used: server1 and server2. You can configure more properties of
- * each server, such as `persistent`, `weight`, `timeout`. Please see [[MemCacheServer]] for available options.
- *
- * @property \Memcache|\Memcached $memCache The memcache instance (or memcached if [[useMemcached]] is true) used by this component.
- * @property MemCacheServer[] $servers List of memcache server configurations.
- *
  * @author Carsten Brandt <mail@cebe.cc>
  * @since 2.0
  */
diff --git a/tests/unit/framework/caching/CacheTest.php b/tests/unit/framework/caching/CacheTest.php
index 021a03c..2ce03a1 100644
--- a/tests/unit/framework/caching/CacheTest.php
+++ b/tests/unit/framework/caching/CacheTest.php
@@ -29,6 +29,16 @@ abstract class CacheTest extends TestCase
 		return $cache;
 	}
 
+	/**
+	 * default value of cache prefix is application id
+	 */
+	public function testKeyPrefix()
+	{
+		$cache = $this->getCacheInstance();
+		$this->assertNotNull(\Yii::$app->id);
+		$this->assertEquals(\Yii::$app->id, $cache->keyPrefix);
+	}
+
 	public function testSet()
 	{
 		$cache = $this->getCacheInstance();