Validation failed: Upload file has an extension that does not match its contents

Question

I am using paperclip gem to upload files. and my paperclip gem version is paperclip-4.1.1. While uploading a file its throwing

Validation failed: Upload file has an extension that does not match its contents.

I am trying to upload a xlsx file. and also i have mentioned that into the model content_type.

 validates_attachment_content_type :upload_file, :content_type => %w(application/msword application/vnd.ms-office application/vnd.ms-excel application/vnd.openxmlformats-officedocument.spreadsheetml.sheet),
                                               :message => ', Only XML,EXCEL files are allowed. '

I don't know why this error is happening. If you have any idea about this error please share.

Excerpt from log to show validation failure:

Command :: file -b --mime-type '/tmp/5249540099071db4e41e119388e9dd6220140513-24023-1jlg4zy' [paperclip] Content Type Spoof: Filename file_for_bulk_upload1.xlsx (["application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"]), content type discovered from file command: . See documentation to allow this combination. 
Command :: file -b --mime-type '/tmp/6f19a4f96154ef7ce65db1d585abdb2820140513-24023-tt4u1e' [paperclip] Content Type Spoof: Filename file_for_bulk_upload1.xlsx (["application/vnd.openxmlformats-officedocument.spreadsheetml.sheet"]), content type discovered from file command: