diff --git a/system/helpers/file_helper.php b/system/helpers/file_helper.php
index 7a35c3f..4434494 100644
--- a/system/helpers/file_helper.php
+++ b/system/helpers/file_helper.php
@@ -352,7 +352,7 @@
 
 		if ( ! is_array($mimes))
 		{
-			if (is_file(APPPATH.'config/'.ENVIRONMENT.'/mimes'.EXT))
+			if (defined('ENVIRONMENT') AND is_file(APPPATH.'config/'.ENVIRONMENT.'/mimes'.EXT))
 			{
 				include(APPPATH.'config/'.ENVIRONMENT.'/mimes'.EXT);
 			}