FileValidator issue with uppercase extensions

[neoacevedo]

When I upload a file with its extension in uppercase, for instance .PNG, although in the validation rule I have set 'extensions' => 'png, jpg, jpeg', 'mimeTypes' => 'image/png, image/jpg, image/jpeg', when I upload a file with uppercase extension, the validation raises the error Only files with these extensions are allowed: png, jpg, jpeg regardless if I set the extensions in lowercase and uppercase.