Thank you for clearing that up - I have always been confused when pcwalton has written (a bunch of times) that &quot;Nim&#x27;s GC isn&#x27;t thread safe&quot; - since... I knew about the deep serialization and couldn&#x27;t for my life understand why it wouldn&#x27;t be safe then.<p>But how could the segfaults then happen? Aha, you mean the test code perhaps shared via globals?