diff --git a/system/libraries/Upload.php b/system/libraries/Upload.php
index ff34615..506d158 100644
--- a/system/libraries/Upload.php
+++ b/system/libraries/Upload.php
@@ -1042,7 +1042,7 @@
 		if (function_exists('mime_content_type'))
 		{
 			$this->file_type = @mime_content_type($file['tmp_name']);
-			if (strlen($this->file_type) > 0) // Turned out it's possible ...
+			if (strlen($this->file_type) > 0) // Turns out it's possible that mime_content_type() returns FALSE or an empty string
 			{
 				return;
 			}