Hi everyone, For a while now (since 10.8) I've been using dispatch_sources to read from serial ports. Up until 10.11.6 everything has been fine, but on 10.12.0 the source's event handler is not always being called when data is available for reading. I see it called a few times, but it often "stops" being called after a second or two - especially if new data has arrived on the serial port. If the source's file descriptor happens to be a regular file, and not a serial port, everything continues to behave as expected. Has anybody else experienced something similar to this? I can provide a short code sample that exemplifies the issue, but you'll need a serial device sending data to the serial port in order to test it. Thanks in advance! /Hans