Скрепки для загрузки офисных файлов (docx,pptx) загружаются в виде zip-файлов?

Для загрузки файлов я использую следующее: Rails 3.2, Paperclip (3.0.4), aws-sdk (1.5.2) и jQuery-File-Upload

Проблема в том, офисные файлы, такие как (pptx), загружаются в виде zip-файлов, а не файлов pptx. Вот что я вижу в логах:

Started POST
Processing by AttachmentsController#create as JS
  Parameters: {"files"=>[#<ActionDispatch::Http::UploadedFile:0x007fa1d5bee960 @original_filename="test1.pptx", @content_type="application/vnd.openxmlformats-officedocument.presentationml.presentation", @headers="Content-Disposition: form-data; name=\"files[]\"; filename=\"test1.pptx\"\r\nContent-Type: application/vnd.openxmlformats-officedocument.presentationml.presentation\r\n", @tempfile=#<File:/var/folders/rm/89l_3yt93g31p22738hqydmr0000gn/T/RackMultipart20120529-10443-1ljhigq>>]}
.....


SQL (1.4ms)  INSERT INTO "attachments" ("attachment_content_type", "attachment_file_name", "attachment_file_size", "attachment_file_title", "attachment_updated_at", "created_at", "deleted", "room_id", "pinned", "updated_at", "user_id") VALUES ($1, $2, $3, $4, $5, $6, $7, $8, $9, $10, $11) RETURNING "id"  [["attachment_content_type", "application/zip"], ["attachment_file_name", "test1_1338339249.pptx"], ["attachment_file_size", 150329], ["attachment_file_title", "test1.pptx"], ["attachment_updated_at", Wed, 30 May 2012 00:54:09 UTC +00:00], ["created_at", Wed, 30 May 2012 00:54:09 UTC +00:00], ["deleted", false], ["room_id", 20], ["pinned", false], ["updated_at", Wed, 30 May 2012 00:54:09 UTC +00:00], ["user_id", 1]]
[paperclip] Saving attachments.
[paperclip] saving /development/private/rooms/20/user_uploaded_files/test1_1338339249.pptx
Command :: file -b --mime '/var/folders/rm/89l_3yt93g31p22738hqydmr0000gn/T/RackMultipart20120529-10443-1ljhigq20120529-10443-1lr2yg2'
[AWS S3 200 1.16513 0 retries] put_object(:acl=>:private,:bucket_name=>"cdn-assets-site-com",:content_type=>"application/zip",:data=>#<Paperclip::FileAdapter:0x007fa1d2540170 @target=#<File:/var/folders/rm/89l_3yt93g31p22738hqydmr0000gn/T/RackMultipart20120529-10443-1ljhigq>, @tempfile=#<File:/var/folders/rm/89l_3yt93g31p22738hqydmr0000gn/T/RackMultipart20120529-10443-1ljhigq20120529-10443-1lr2yg2>>,:key=>"development/private/rooms/20/user_uploaded_files/test1_1338339249.pptx") 

Обратите внимание, что файл приходит в формате pptx, но при загрузке на AWS S3 идет как zip-файл?