diff --git a/system/core/CodeIgniter.php b/system/core/CodeIgniter.php
index 8159b19..f3592ea 100644
--- a/system/core/CodeIgniter.php
+++ b/system/core/CodeIgniter.php
@@ -50,7 +50,7 @@
  *  Load the global functions
  * ------------------------------------------------------
  */
-	require(BASEPATH.'core/Common.php');
+	require_once(BASEPATH.'core/Common.php');
 
 /*
  * ------------------------------------------------------
diff --git a/system/core/Common.php b/system/core/Common.php
index 981af45..341402c 100644
--- a/system/core/Common.php
+++ b/system/core/Common.php
@@ -150,7 +150,7 @@
 
 				if (class_exists($name) === FALSE)
 				{
-					require($path.$directory.'/'.$class.'.php');
+					require_once($path.$directory.'/'.$class.'.php');
 				}
 
 				break;
@@ -164,7 +164,7 @@
 
 			if (class_exists($name) === FALSE)
 			{
-				require(APPPATH.$directory.'/'.config_item('subclass_prefix').$class.'.php');
+				require_once(APPPATH.$directory.'/'.config_item('subclass_prefix').$class.'.php');
 			}
 		}