Hello, In the chapter about synchronization in the boost.thread documentation, where the hello world example with the bank account is being shown, I see a small problem in the class: int GetBalance() { mtx_.lock(); int b = balance_; mtx_.unlock(); return balance_; } I believe it should be: int GetBalance() { mtx_.lock(); int b = balance_; mtx_.unlock(); return b; } Kind regards, Philip Bennefall