I have previously used Boost.Units and autoscaled using << engineering_prefix nicely, and this works as expected for quantity of type double. but it seems that code that I believe worked previously does not autoscale when using a *user-defined type*, like the measurement example in kitchen_sink.cpp. To confirm this, I have added after //[kitchen_sink_snippet_8 in kitchen_sink.cpp at line 445 a measurement quantity where the length is long enough to trigger conversion to km, thus quantity<length,measurement<double> > biglen(measurement<double>(12345.0,123.0)*meters); std::cout << "Biglen autoscaled "<< engineering_prefix << biglen << std::endl; but I get a *unscaled* value :-( Biglen autoscaled 12345(+/-123) m rather than the expected conversion to kilometers 12.345(+/- 0.123) km Am I doing something wrong, or has something changed? Thanks Paul PS Using Microsoft Visual Studio 2010 Version 10.0.40219.1 SP1Rel Microsoft .NET Framework Version 4.0.30319 SP1Rel Boost-trunk (Boost.1.49) --- Paul A. Bristow, Prizet Farmhouse, Kendal LA8 8AB UK +44 1539 561830 07714330204 pbristow@hetp.u-net.com