In this bug https://bugzilla.netfilter.org/show_bug.cgi?id=1444 The segfault occurs when set_ref_expr_print() calls expr_print() with expr->set->init as its argument because there is no space allocated for expr->set->init. See: http://git.netfilter.org/nftables/tree/src/expression.c#n1209 Will a simple if-check for expr->set->init be an appropriate solution for this? Thanks