Upload column - Updating the image using upload_column

Hai I am using upload_column for uploading images. Trying to do the user registration. For the first time when the user tries to upload image it works fine. But when try to update the image an error undefined method `process!' for #<UploadColumn::UploadedFile:0x6838424> occurs. in my view I set the multipart=>true. and in controller in the edit action @user = User.find(params[:id]) and in update action @user.update_attributes(params[:user]). Do I need to add anything more? Please help , thanks in advance