Hi Sven & Alastair, Thanks a lot for this bugreport and the quick fix!
I've asked Slang's author to release version 2.3.2 in the near future to officially fix this issue, and he agreed to do so at the end of this month. See [1]. If that indeed happens, upgrading to 2.3.2 would be a cleaner, official fix, allowing you to drop the patch. Let's keep an eye on it. Cheers, egmont [1] http://lists.jedsoft.org/lists/slang-users/2018/0000000.html