missing a cast for the `bind` call

sockaddr-cast.txt

[~/src/SillyMUD/src]$ make
gcc -g -DIMPL_SECURITY -DNEW_RENT -DLEVEL_LOSS -DNEWEXP -DGROUP_NAMES -Werror -DIMPL_SECURITY -DNEW_RENT -DLEVEL_LOSS -DNEWEXP -DGROUP_NAMES  -c -o comm.o comm.c
comm.c:755:14: error: incompatible pointer types passing 'struct sockaddr_in *'
      to parameter of type 'const struct sockaddr *'
      [-Werror,-Wincompatible-pointer-types]
        if (bind(s, &sa, sizeof(sa)) < 0)       {
                    ^~~
/usr/include/sys/socket.h:557:38: note: passing argument to parameter here
int     bind(int, const struct sockaddr *, socklen_t) __DARWIN_ALIAS(bind);
                                         ^
...
9 errors generated.
make: *** [comm.o] Error 1