Case of File Type

When posting a file to Zoho editor, I have seen an issue where if the filetype (format) is "DOC", rather than "doc". The editor cannot save the file back to my application. When I post the same file with a format of "doc" the file works perfectly.

I get a message stating format is not supported.
(Document format not supported. Error in saving content)

Has anyone had any issues of this type? Any workarounds? Is this a bug?