diff --git a/system/libraries/Cache/Cache.php b/system/libraries/Cache/Cache.php
index e1089f7..537897e 100644
--- a/system/libraries/Cache/Cache.php
+++ b/system/libraries/Cache/Cache.php
@@ -106,7 +106,7 @@
 
 		isset($config['key_prefix']) && $this->key_prefix = $config['key_prefix'];
 
-		if (isset($config['backup']) && in_array('cache_'.$config['backup'], $this->valid_drivers))
+		if (isset($config['backup']) && in_array($config['backup'], $this->valid_drivers))
 		{
 			$this->_backup_driver = $config['backup'];
 		}
@@ -123,6 +123,7 @@
 			else
 			{
 				// Backup is supported. Set it to primary.
+				log_message('debug', 'Cache adapter "'.$this->_adapter.'" is unavailable. Falling back to "'.$this->_backup_driver.'" backup adapter.');
 				$this->_adapter = $this->_backup_driver;
 			}
 		}