FIR SED of SDSS J1148+5251, where only the continuum measurements corrected for the contaminating north-west source are shown, i.e. the Herschel/PACS observations by Leipski et al. (2013), the PdBI observations by Riechers et al. (2009) and Gallerani et al. (2014), and our new PdBI observations at 256 GHz (Sect. 3.1). Different symbols have been used for different datasets (see legend at the bottom-left corner of the plot). The FIR SED has been fit with a single dust temperature modified blackbody with fixed emissivity β = 1.6, combined with a MIR power law, following Casey (2012). Our new PdBI data point at 256 GHz has been excluded from the fit, as explained in the text.