diff --git a/system/core/CodeIgniter.php b/system/core/CodeIgniter.php
index cb4b735..7f76977 100644
--- a/system/core/CodeIgniter.php
+++ b/system/core/CodeIgniter.php
@@ -263,7 +263,7 @@
 	$class  = $RTR->fetch_class();
 	$method = $RTR->fetch_method();
 
-	if ( ! class_exists($class) OR $method[0] === '_' OR method_exists('CI_Controller', $method))
+	if ( ! class_exists($class, FALSE) OR $method[0] === '_' OR method_exists('CI_Controller', $method))
 	{
 		if ( ! empty($RTR->routes['404_override']))
 		{
@@ -272,7 +272,7 @@
 				$method = 'index';
 			}
 
-			if ( ! class_exists($class))
+			if ( ! class_exists($class, FALSE))
 			{
 				if ( ! file_exists(APPPATH.'controllers/'.$class.'.php'))
 				{
@@ -310,7 +310,7 @@
 				$method = 'index';
 			}
 
-			if ( ! class_exists($class))
+			if ( ! class_exists($class, FALSE))
 			{
 				if ( ! file_exists(APPPATH.'controllers/'.$class.'.php'))
 				{
diff --git a/system/core/Common.php b/system/core/Common.php
index f8c1290..ee9bb2e 100644
--- a/system/core/Common.php
+++ b/system/core/Common.php
@@ -149,7 +149,7 @@
 			{
 				$name = $prefix.$class;
 
-				if (class_exists($name) === FALSE)
+				if (class_exists($name, FALSE) === FALSE)
 				{
 					require_once($path.$directory.'/'.$class.'.php');
 				}
@@ -163,7 +163,7 @@
 		{
 			$name = config_item('subclass_prefix').$class;
 
-			if (class_exists($name) === FALSE)
+			if (class_exists($name, FALSE) === FALSE)
 			{
 				require_once(APPPATH.$directory.'/'.config_item('subclass_prefix').$class.'.php');
 			}
diff --git a/system/core/Hooks.php b/system/core/Hooks.php
index 17f6a02..b3b1119 100644
--- a/system/core/Hooks.php
+++ b/system/core/Hooks.php
@@ -195,7 +195,7 @@
 		// Call the requested class and/or function
 		if ($class !== FALSE)
 		{
-			if ( ! class_exists($class))
+			if ( ! class_exists($class, FALSE))
 			{
 				require($filepath);
 			}
diff --git a/system/core/Loader.php b/system/core/Loader.php
index 9306a09..6e5b58b 100644
--- a/system/core/Loader.php
+++ b/system/core/Loader.php
@@ -270,7 +270,7 @@
 				continue;
 			}
 
-			if ($db_conn !== FALSE && ! class_exists('CI_DB'))
+			if ($db_conn !== FALSE && ! class_exists('CI_DB', FALSE))
 			{
 				if ($db_conn === TRUE)
 				{
@@ -280,7 +280,7 @@
 				$CI->load->database($db_conn, FALSE, TRUE);
 			}
 
-			if ( ! class_exists('CI_Model'))
+			if ( ! class_exists('CI_Model', FALSE))
 			{
 				load_class('Model', 'core');
 			}
@@ -1091,11 +1091,11 @@
 
 		if ($prefix === '')
 		{
-			if (class_exists('CI_'.$class))
+			if (class_exists('CI_'.$class, FALSE))
 			{
 				$name = 'CI_'.$class;
 			}
-			elseif (class_exists(config_item('subclass_prefix').$class))
+			elseif (class_exists(config_item('subclass_prefix').$class, FALSE))
 			{
 				$name = config_item('subclass_prefix').$class;
 			}
@@ -1110,7 +1110,7 @@
 		}
 
 		// Is the class name valid?
-		if ( ! class_exists($name))
+		if ( ! class_exists($name, FALSE))
 		{
 			log_message('error', 'Non-existent class: '.$name);
 			show_error('Non-existent class: '.$name);
diff --git a/system/core/Output.php b/system/core/Output.php
index a208414..25ecd49 100644
--- a/system/core/Output.php
+++ b/system/core/Output.php
@@ -395,7 +395,7 @@
 		global $BM, $CFG;
 
 		// Grab the super object if we can.
-		if (class_exists('CI_Controller'))
+		if (class_exists('CI_Controller', FALSE))
 		{
 			$CI =& get_instance();
 		}
diff --git a/system/database/DB.php b/system/database/DB.php
index d910474..83d9733 100644
--- a/system/database/DB.php
+++ b/system/database/DB.php
@@ -149,7 +149,7 @@
 	if ( ! isset($query_builder) OR $query_builder === TRUE)
 	{
 		require_once(BASEPATH.'database/DB_query_builder.php');
-		if ( ! class_exists('CI_DB'))
+		if ( ! class_exists('CI_DB', FALSE))
 		{
 			/**
 			 * CI_DB
@@ -162,7 +162,7 @@
 			class CI_DB extends CI_DB_query_builder { }
 		}
 	}
-	elseif ( ! class_exists('CI_DB'))
+	elseif ( ! class_exists('CI_DB', FALSE))
 	{
 		/**
 	 	 * @ignore
diff --git a/system/database/DB_driver.php b/system/database/DB_driver.php
index 35ac8e8..213e2c3 100644
--- a/system/database/DB_driver.php
+++ b/system/database/DB_driver.php
@@ -704,7 +704,7 @@
 	{
 		$driver = 'CI_DB_'.$this->dbdriver.'_result';
 
-		if ( ! class_exists($driver))
+		if ( ! class_exists($driver, FALSE))
 		{
 			include_once(BASEPATH.'database/DB_result.php');
 			include_once(BASEPATH.'database/drivers/'.$this->dbdriver.'/'.$this->dbdriver.'_result.php');
@@ -1560,7 +1560,7 @@
 	 */
 	protected function _cache_init()
 	{
-		if (class_exists('CI_DB_Cache'))
+		if (class_exists('CI_DB_Cache', FALSE))
 		{
 			if (is_object($this->CACHE))
 			{
diff --git a/system/libraries/Cache/drivers/Cache_memcached.php b/system/libraries/Cache/drivers/Cache_memcached.php
index 8096b26..246a7a2 100644
--- a/system/libraries/Cache/drivers/Cache_memcached.php
+++ b/system/libraries/Cache/drivers/Cache_memcached.php
@@ -182,11 +182,11 @@
 			}
 		}
 
-		if (class_exists('Memcached'))
+		if (class_exists('Memcached', FALSE))
 		{
 			$this->_memcached = new Memcached();
 		}
-		elseif (class_exists('Memcache'))
+		elseif (class_exists('Memcache', FALSE))
 		{
 			$this->_memcached = new Memcache();
 		}
diff --git a/system/libraries/Migration.php b/system/libraries/Migration.php
index b673e9c..cc6fe48 100644
--- a/system/libraries/Migration.php
+++ b/system/libraries/Migration.php
@@ -228,7 +228,7 @@
 			$class = 'Migration_'.ucfirst(strtolower($this->_get_migration_name(basename($file, '.php'))));
 
 			// Validate the migration file structure
-			if ( ! class_exists($class))
+			if ( ! class_exists($class, FALSE))
 			{
 				$this->_error_string = sprintf($this->lang->line('migration_class_doesnt_exist'), $class);
 				return FALSE;
diff --git a/system/libraries/Xmlrpcs.php b/system/libraries/Xmlrpcs.php
index d4524d2..d263d78 100644
--- a/system/libraries/Xmlrpcs.php
+++ b/system/libraries/Xmlrpcs.php
@@ -31,7 +31,7 @@
 	show_error('Your PHP installation does not support XML');
 }
 
-if ( ! class_exists('CI_Xmlrpc'))
+if ( ! class_exists('CI_Xmlrpc', FALSE))
 {
 	show_error('You must load the Xmlrpc class before loading the Xmlrpcs class in order to create a server.');
 }