I figured out what my problem was: When constructing a boost::mutex::scoped_lock in 1.33 the second parameter is a boolean. In 1.38, boost::mutex::scoped_lock (defined as unique_lock) constructor is overloaded using different types as the initial lock state instead of a single constructor with a boolean. In the constructor I now have to use adopt_lock_t, defer_lock_t, or try_to_lock_t as the second parameter. In 1.33: boost::mutex mtx; boost::mutex::scoped_lock lock(mtx, false); In 1.38 now looks like: boost::mutex mtx; boost::mutex::scoped_lock lock(mtx, defer_lock_t()); -Tom -- View this message in context: http://www.nabble.com/Compilation-errors-upgrading-boost-from-1.34-to-1.37-%... Sent from the Boost - Dev mailing list archive at Nabble.com.