diff --git a/system/libraries/Upload.php b/system/libraries/Upload.php
index 5816a55..3cd2e4f 100644
--- a/system/libraries/Upload.php
+++ b/system/libraries/Upload.php
@@ -951,7 +951,7 @@
 
 		if (count($this->mimes) == 0)
 		{
-			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);
 			}