Hi all, The following does not compile (GCC 4.2): #include <boost/logic/tribool.hpp> template<typename T> void byRef( const T& v ) { } // ... byRef( boost::indeterminate ); I realise that indeterminate is actually a function. If I write my own, equivalent, function I can substitute it here and it compiles, however. I can't see what is stopping it from working in indeterminate's case - but I suspect it is to do with some of the operator overloading going on. I couldn't pin it down, though. I can take it by value, of course. What am I missing? Before you ask - yes this is boiled down code. In my real situation I have generic code that doesn't even know about tribool, so I can't special-case it. And I'd rather get to the bottom of why it doesn't work for me - even if the end result is "you can't do that". Thanks and regards, [)o IhIL..