  We report on submillimetre observations of three high redshift (z>6) quasars,
made using the SCUBA camera on the JCMT. Only one of the sample was detected at
850um-- SDSS J1148+5251 (z=6.43). It was also detected (>3 sigma significance)
at 450um, one of the few z>4 quasars for which this is the case. In combination
with existing millimetric data, the submm detections allow us to place limits
on the temperature of the submm-emitting dust, hence on the mass of dust to be
synthesized under the time constraint imposed by the quasar's redshift.
