diff --git a/include/qbsp/qbsp.hh b/include/qbsp/qbsp.hh
index 69a0efc6..1d961c96 100644
--- a/include/qbsp/qbsp.hh
+++ b/include/qbsp/qbsp.hh
@@ -666,8 +666,8 @@ struct node_t
     uint32_t firstleafbrush; // Q2
     uint32_t numleafbrushes;
     int32_t area;
-    std::set<bspbrush_t *, bspbrush_t_less> original_brushes; // FIXME: only valid during construction
-    std::unordered_set<const mapbrush_t *> original_mapbrushes;
+    std::vector<bspbrush_t *> original_brushes; // FIXME: only valid during construction
+    std::vector<const mapbrush_t *> original_mapbrushes;
 };
 
 void InitQBSP(int argc, const char **argv);
diff --git a/qbsp/brushbsp.cc b/qbsp/brushbsp.cc
index a1449de0..b70571cd 100644
--- a/qbsp/brushbsp.cc
+++ b/qbsp/brushbsp.cc
@@ -388,8 +388,7 @@ static void LeafNode(node_t *leafnode, std::vector<std::unique_ptr<bspbrush_t>>
     }
     for (auto &brush : brushes) {
         Q_assert(brush->original != nullptr);
-        leafnode->original_brushes.insert(brush->original);
-        leafnode->original_mapbrushes.insert(brush->original->mapbrush);
+        leafnode->original_brushes.push_back(brush->original);
     }
 
     qbsp_options.target_game->count_contents_in_stats(leafnode->contents, *stats.leafstats);
diff --git a/qbsp/tree.cc b/qbsp/tree.cc
index 08690cf5..1b02e3cc 100644
--- a/qbsp/tree.cc
+++ b/qbsp/tree.cc
@@ -78,10 +78,24 @@ void FreeTreePortals(tree_t *tree)
 static void ConvertNodeToLeaf(node_t *node, const contentflags_t &contents)
 {
     // merge the children's brush lists
-    node->original_mapbrushes = node->children[0]->original_mapbrushes;
-    node->original_mapbrushes.insert(node->children[1]->original_mapbrushes.begin(), node->children[1]->original_mapbrushes.end());
+    node->original_brushes = std::move(node->children[0]->original_brushes);
+    node->original_brushes.insert(node->original_brushes.end(), node->children[1]->original_brushes.begin(), node->children[1]->original_brushes.end());
 
-    node->original_brushes.clear();
+    if (node->original_brushes.size()) {
+        std::sort(node->original_brushes.begin(), node->original_brushes.end(), bspbrush_t_less());
+        auto unique_begin = std::unique(node->original_brushes.begin(), node->original_brushes.end());
+        node->original_brushes.erase(unique_begin, node->original_brushes.end());
+
+        // migrate it over to mapbrushes
+        node->original_mapbrushes.reserve(node->original_brushes.size());
+
+        for (auto &b : node->original_brushes) {
+            node->original_mapbrushes.push_back(b->mapbrush);
+        }
+
+        // clear original_brushes since we no longer need it
+        node->original_brushes.clear();
+    }
 
     node->is_leaf = true;
 
@@ -99,7 +113,6 @@ static void ConvertNodeToLeaf(node_t *node, const contentflags_t &contents)
 static void PruneNodes_R(node_t *node, std::atomic<int32_t> &count_pruned)
 {
     if (node->is_leaf) {
-        node->original_brushes.clear();
         return;
     }