fcntl() + Blocking

http://www.cplusplus.com/forum/unices/10016/

fcntl(fd, F_SETFL, O_NONBLOCK);

I have set up a socket file descriptor to non-blocking mode using fcntl() function call. Now how do I set this back to blocking mode?

int flags = fcntl(fd, F_GETFL);
int result = fcntl(fd, F_SETFL, flags & ~O_NONBLOCK);