Asset file properties are nil when using sync

[neonichu]

An asset retrieved via sync looks like this:

#<Contentful::Asset: @fields={:title=>"{\"en-US\"=>\"Doge\"}", :file=>#<Contentful::File: @properties={:fileName=>nil, :contentType=>nil, :details=>nil, :url=>nil}>, :description=>"{\"en-US\"=>\"nice picture\"}"} @sys={:space=>#<Contentful::Link: @sys={:type=>"Link", :linkType=>"Space", :id=>"cfexampleapi"}>, :type=>"Asset", :id=>"1x0xpXu4pSGS4OukSyWGUK", :revision=>6, :createdAt=>#<DateTime: 2013-11-06T09:45:10+00:00 ((2456603j,35110s,0n),+0s,2299161j)>, :updatedAt=>#<DateTime: 2013-12-18T13:27:14+00:00 ((2456645j,48434s,917000000n),+0s,2299161j)>}>

Obviously, the file properties should not be nil.