I'm not sure if there's a more appropriate venue to bring this up; the package doesn't seem to have any sort of explicit issue tracker. On the NixOS build servers, we're seeing across-the-board failures for the 0.4.2.0 release of the 'tar' library, specifically, two properties that were added in the latest release. It looks to me like prop_lookup is fundamentally broken---it falls over in the face of a lookup for 'a/b' in a list of entries that includes 'a/b/c/d', because while the library lookup function returns a match including the remainder of the path as a result, the Data.List.lookup that it's comparing against returns nothing. I don't see a way for the test as it is constituted to work reliably. I'm going to guess that prop_valid suffers from a similar issue. Either way, it would be nice if they could either be corrected, or diked out until that happens. Mike.