@abcdw Hi, there seem to be exceptions. "Ports should be closed when they are not needed .... Any error that occurs while writing out that buffered data would also be raised promptly at the close-port, and not later when the port is closed by the garbage collector." https://www.gnu.org/software/guile/manual/html_node/Ports.html "Buffered writes defer error detection (and defer the side effects to the mutable store), perhaps indefinitely if the port type does not need to be closed at GC." https://www.gnu.org/software/guile/manual/html_node/Buffering.html