File_column validation ignored

I'm using the file_column plugin to upload a small avatar, but when I
do this:

@user.update_attribute("picture", params[:user][:picture])

... it completely ignores the validations I've set for the element
before:

validates_file_format_of :picture, :in => ["gif", "jpg", "png"]
validates_filesize_of :picture, :in => 1.kilobytes..100.kilobytes

I'm able to upload PDF's, textfiles, etc., which is ofcourse rather
crappy. I've added this to my model, in case you're wondering:

file_column :picture, :base_url => "images/people", :filename =>
"picture", :store_dir => "public/images/people/",
   :magick => {
    :size => '48x48!',
    :crop => '1:1',
    :versions => {
      :thumb => {:crop => "1:1", :size => "16x16!", :name => "thumb"}
    }
  }

Has anybody else experienced this problem?

Bump :slight_smile:

Anybody?

I've tried including validations.rb in my setup, but that also does
not work.