ruby-on-rails – 办公文件(docx,pptx)的PaperClip上传作为zip文

问题是办公室文件(pptx)正在下载为zip文件而不是pptx文件.这是我在日志中看到的：

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"rnContent-Type: application/vnd.openxmlformats-officedocument.presentationml.presentationrn",@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",["deleted",false],["room_id",20],["pinned",["updated_at",["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")

注意文件如何以pptx的形式出现,但是当上传到AWS S3时,可以将其作为zip文件？