Upper limits on [C/Fe] for SDSS J102915+172927. The 1D LTE and 3D LTE results are shown as triangles and squares, respectively, for the original limits (Caffau et al. 2012, red) and the results of this work (blue). For comparison, we show the [C/Fe] abundance for a sample of metal-poor stars from the SAGA database (Suda et al. 2008, black circles) and the cut-off for carbon-enhancement at [C/Fe] = 0.7 (dotted line) from Aoki et al. (2007).