Thanks for the info. This is illegal code. That it compiled in MSVC 7.0 was a bug. The template parameter '_Source' can not be deduced from the callsite of doSomething. 14.8.2.4 in the ISO/IEC 14882 lists the forms in which template parameters can be deduced, but a qualified name involving nested types is not one of them. I suspect it's because of something like this: [Non-text portions of this message have been removed]