Hi, the return value of read is ssize_t and not size_t. I guess you mean if (*fd >= 0) in dbus-sysdeps-unix.c:89. fd alone is always >= 0. If pending_return in line dbus-connection.c:2641 is NULL, then the condition in line 2646 should not become true. Otherwise line 2650 crashes. Greetings Christoph