Aspect scaling not working with HD4600 + DP ?

Aspect scaling seems to be broken with the following configuration:

Hardware:

Intel Core i7-4790K (HD4600)

Display connected via DisplayLink -> DP-to-DVI converter -> DVI-Port of display

Mainboard: Asus Sabertooth Mark2 (Z97) if of any interest.

Software:

Arch Linux

Kernel 3.17

xf86-video-intel 2.99.916

xorg-server 1.16.1

libxrandr 1.4.2

Here's what xrandr tells me:

$ xrandr --props
Screen 0: minimum 320 x 200, current 2560 x 1600, maximum 8192 x 8192
VGA1 disconnected (normal left inverted right x axis y axis)
DP1 connected 2560x1600+0+0 (normal left inverted right x axis y axis) 646mm x 406mm
        EDID: 
                00ffffffffffff004c2d360230335548
                151101038040287828fe87a3574a9c25
                13505400000001010101010101010101
                010101010101bc1b00a0502017303020
                360086962100001ab06800a0a0402e60
                3020360086962100001a000000fc0053
                796e634d61737465720a2020000000ff
                00485335503530303530380a2020005a
        Broadcast RGB: Automatic 
                supported: Automatic, Full, Limited 16:235
        audio: auto 
                supported: force-dvi, off, auto, on
   2560x1600     59.86* 
   1280x800      59.91  
HDMI1 disconnected (normal left inverted right x axis y axis)
        aspect ratio: Automatic 
                supported: Automatic, 4:3, 16:9
        Broadcast RGB: Automatic 
                supported: Automatic, Full, Limited 16:235
        audio: auto 
                supported: force-dvi, off, auto, on
HDMI2 disconnected (normal left inverted right x axis y axis)
        aspect ratio: Automatic 
                supported: Automatic, 4:3, 16:9
        Broadcast RGB: Automatic 
                supported: Automatic, Full, Limited 16:235
        audio: auto 
                supported: force-dvi, off, auto, on

$ xrandr --output DP1 --set "scaling mode" "Full aspect"
X Error of failed request:  BadName (named color or font does not exist)
  Major opcode of failed request:  140 (RANDR)
  Minor opcode of failed request:  11 (RRQueryOutputProperty)
  Serial number of failed request:  34
  Current serial number in output stream:  34

$ xrandr --output DP1 --set PANEL_FITTING full_aspect
X Error of failed request:  BadName (named color or font does not exist)
  Major opcode of failed request:  140 (RANDR)
  Minor opcode of failed request:  11 (RRQueryOutputProperty)
  Serial number of failed request:  34
  Current serial number in output stream:  34