diff --git a/library/include/DataIdentity.h b/library/include/DataIdentity.h
index ed4ca06ecd..4bd4976250 100644
--- a/library/include/DataIdentity.h
+++ b/library/include/DataIdentity.h
@@ -840,7 +840,7 @@ namespace df
     template<class T>
     inline const container_identity* identity_traits<std::unordered_set<T> >::get()
     {
-        using container = std::set<T>;
+        using container = std::unordered_set<T>;
         static const ro_stl_container_identity<container> identity("unordered_set", identity_traits<T>::get());
         return &identity;
     }
diff --git a/plugins/sort.cpp b/plugins/sort.cpp
index add54688c4..9b91f1118c 100644
--- a/plugins/sort.cpp
+++ b/plugins/sort.cpp
@@ -1,3 +1,5 @@
+#include <variant>
+
 #include "Debug.h"
 #include "LuaTools.h"
 #include "PluginManager.h"
@@ -25,7 +27,7 @@ namespace DFHack {
     DBG_DECLARE(sort, log, DebugCategory::LINFO);
 }
 
-using item_or_unit = std::pair<void *, bool>;
+using item_or_unit = std::variant<df::unit*, df::item*>;
 using filter_vec_type = std::vector<std::function<bool(item_or_unit)>>;
 
 // recreated here since our autogenerated df::sort_entry lacks template params
@@ -44,8 +46,8 @@ static bool probing = false;
 static bool probe_result = false;
 
 static bool do_filter(const char *module_name, const char *fn_name, const item_or_unit &elem) {
-    if (elem.second) return true;
-    auto unit = (df::unit *)elem.first;
+    if (std::holds_alternative<df::item*>(elem)) return true;
+    auto unit = std::get<df::unit*>(elem);
 
     if (probing) {
         TRACE(log).print("probe successful\n");
@@ -78,11 +80,11 @@ static bool do_work_animal_assignment_filter(item_or_unit elem) {
 
 static int32_t our_filter_idx(df::widget_unit_list *unitlist) {
     if (world->units.active.empty())
-        return true;
+        return -1;
 
     df::unit *u = world->units.active[0]; // any unit will do; we just need a sentinel
     if (!u)
-        return true;
+        return -1;
 
     probing = true;
     probe_result = false;
@@ -91,8 +93,8 @@ static int32_t our_filter_idx(df::widget_unit_list *unitlist) {
     filter_vec_type *filter_vec = reinterpret_cast<filter_vec_type *>(&unitlist->filter_func);
 
     TRACE(log).print("probing for our filter function\n");
-    for (auto fn : *filter_vec) {
-        fn(std::make_pair(u, false));
+    for (auto& fn : *filter_vec) {
+        fn(item_or_unit(u));
         if (probe_result) {
             TRACE(log).print("found our filter function at idx %d\n", idx);
             break;
@@ -144,13 +146,13 @@ static df::widget_unit_list * get_work_animal_assignment_unit_list() {
 //
 
 static bool sort_proxy(const item_or_unit &a, const item_or_unit &b) {
-    if (a.second || b.second)
+    if (std::holds_alternative<df::item*>(a) || std::holds_alternative<df::item*>(b))
         return true;
 
     bool ret = true;
     color_ostream &out = Core::getInstance().getConsole();
     Lua::CallLuaModuleFunction(out, "plugins.sort", "do_sort",
-        std::make_tuple((df::unit *)a.first, (df::unit *)b.first),
+        std::make_tuple(std::get<df::unit*>(a), std::get<df::unit*>(b)),
         1, [&](lua_State *L){
             ret = lua_toboolean(L, 1);
         }