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.');
 }