diff --git a/include/qbsp/outside.hh b/include/qbsp/outside.hh
index f8879172..030d546e 100644
--- a/include/qbsp/outside.hh
+++ b/include/qbsp/outside.hh
@@ -22,4 +22,6 @@
 #pragma once
 
 bool FillOutside(mapentity_t *entity, node_t *node, const int hullnum);
-std::vector<node_t *> FindOccupiedClusters(node_t *headnode);
\ No newline at end of file
+std::vector<node_t *> FindOccupiedClusters(node_t *headnode);
+
+void FillBrushEntity(mapentity_t *entity, node_t *node, const int hullnum);
diff --git a/include/qbsp/portals.hh b/include/qbsp/portals.hh
index e2c7cf39..16e7d4b8 100644
--- a/include/qbsp/portals.hh
+++ b/include/qbsp/portals.hh
@@ -35,5 +35,5 @@ struct portal_t
 extern node_t outside_node; // portals outside the world face this
 
 contentflags_t ClusterContents(const node_t *node);
-void PortalizeWorld(const mapentity_t *entity, node_t *headnode, const int hullnum);
+void PortalizeEntity(const mapentity_t *entity, node_t *headnode, const int hullnum);
 void FreeAllPortals(node_t *node);
diff --git a/qbsp/outside.cc b/qbsp/outside.cc
index abcca899..750c552d 100644
--- a/qbsp/outside.cc
+++ b/qbsp/outside.cc
@@ -585,3 +585,15 @@ bool FillOutside(mapentity_t *entity, node_t *node, const int hullnum)
     logging::print(logging::flag::STAT, "     {:8} outleafs\n", outleafs);
     return true;
 }
+
+void FillBrushEntity(mapentity_t* entity, node_t* node, const int hullnum)
+{
+    logging::print(logging::flag::PROGRESS, "---- {} ----\n", __func__);
+
+    // Clear the outside filling state on all nodes
+    ClearOccupied_r(node);
+
+    MarkBrushSidesInvisible(entity);
+
+    MarkVisibleBrushSides_R(node);
+}
diff --git a/qbsp/portals.cc b/qbsp/portals.cc
index d1e403bd..5bfdfd43 100644
--- a/qbsp/portals.cc
+++ b/qbsp/portals.cc
@@ -617,7 +617,7 @@ PortalizeWorld
 Builds the exact polyhedrons for the nodes and leafs
 ==================
 */
-void PortalizeWorld(const mapentity_t *entity, node_t *headnode, const int hullnum)
+void PortalizeEntity(const mapentity_t *entity, node_t *headnode, const int hullnum)
 {
     logging::print(logging::flag::PROGRESS, "---- {} ----\n", __func__);
 
@@ -630,7 +630,7 @@ void PortalizeWorld(const mapentity_t *entity, node_t *headnode, const int hulln
 
     logging::percent(splitnodes, splitnodes, entity == map.world_entity());
 
-    if (hullnum <= 0) {
+    if (hullnum <= 0 && entity == map.world_entity()) {
         /* save portal file for vis tracing */
         WritePortalfile(headnode, &state);
 
diff --git a/qbsp/qbsp.cc b/qbsp/qbsp.cc
index b76ef9b7..6b458da0 100644
--- a/qbsp/qbsp.cc
+++ b/qbsp/qbsp.cc
@@ -699,7 +699,7 @@ static void ProcessEntity(mapentity_t *entity, const int hullnum)
         nodes = SolidBSP(entity, true);
         if (entity == map.world_entity() && !options.nofill.value()) {
             // assume non-world bmodels are simple
-            PortalizeWorld(entity, nodes, hullnum);
+            PortalizeEntity(entity, nodes, hullnum);
             if (FillOutside(entity, nodes, hullnum)) {
                 // fixme-brushbsp: re-add
                 // FreeNodes(nodes);
@@ -732,10 +732,9 @@ static void ProcessEntity(mapentity_t *entity, const int hullnum)
 
         // build all the portals in the bsp tree
         // some portals are solid polygons, and some are paths to other leafs
-        if (entity == map.world_entity()) {
-            // assume non-world bmodels are simple
-            PortalizeWorld(entity, nodes, hullnum);
+        PortalizeEntity(entity, nodes, hullnum);
 
+        if (entity == map.world_entity()) {
             // flood fills from the void.
             // marks brush sides which are *only* touching void;
             // we can skip using them as BSP splitters on the "really good tree"
@@ -748,7 +747,7 @@ static void ProcessEntity(mapentity_t *entity, const int hullnum)
                 nodes = SolidBSP(entity, false);
 
                 // make the real portals for vis tracing
-                PortalizeWorld(entity, nodes, hullnum);
+                PortalizeEntity(entity, nodes, hullnum);
             }
 
             // Area portals
@@ -756,6 +755,11 @@ static void ProcessEntity(mapentity_t *entity, const int hullnum)
                 FloodAreas(entity, nodes);
                 EmitAreaPortals(nodes);
             }
+        } else {
+            FillBrushEntity(entity, nodes, hullnum);
+
+            // rebuild BSP now that we've marked invisible brush sides
+            nodes = SolidBSP(entity, false);
         }
 
         PruneNodes(nodes);