diff --git a/include/qbsp/csg4.hh b/include/qbsp/csg4.hh
index 7bab245e..d1d3d3cd 100644
--- a/include/qbsp/csg4.hh
+++ b/include/qbsp/csg4.hh
@@ -33,6 +33,7 @@ struct face_t;
 
 int MakeSkipTexinfo();
 face_t *NewFaceFromFace(const face_t *in);
+face_t *CopyFace(const face_t *in);
 face_t *MirrorFace(const face_t *face);
 std::tuple<face_t *, face_t *> SplitFace(face_t *in, const qplane3d &split);
 void UpdateFaceSphere(face_t *in);
diff --git a/qbsp/csg4.cc b/qbsp/csg4.cc
index b3a0933f..b22e6606 100644
--- a/qbsp/csg4.cc
+++ b/qbsp/csg4.cc
@@ -86,6 +86,13 @@ face_t *NewFaceFromFace(const face_t *in)
     return newf;
 }
 
+face_t* CopyFace(const face_t* in)
+{
+    face_t *temp = NewFaceFromFace(in);
+    temp->w = in->w;
+    return temp;
+}
+
 void UpdateFaceSphere(face_t *in)
 {
     in->origin = in->w.center();
diff --git a/qbsp/surfaces.cc b/qbsp/surfaces.cc
index 84cbb1a2..9ca28ade 100644
--- a/qbsp/surfaces.cc
+++ b/qbsp/surfaces.cc
@@ -499,19 +499,25 @@ AddMarksurfaces_r
 
 Adds the given face to the markfaces lists of all descendant leafs of `node`.
 
-fixme-brushbsp: do this accurately, not exhaustively
 fixme-brushbsp: all leafs in a cluster can share the same marksurfaces, right?
 ================
 */
-static void AddMarksurfaces_r(face_t *face, node_t *node)
+static void AddMarksurfaces_r(face_t *face, face_t *face_copy, node_t *node)
 {
     if (node->planenum == PLANENUM_LEAF) {
         node->markfaces.push_back(face);
         return;
     }
 
-    AddMarksurfaces_r(face, node->children[0]);
-    AddMarksurfaces_r(face, node->children[1]);
+    const qbsp_plane_t &splitplane = map.planes[node->planenum];
+
+    auto [frontFragment, backFragment] = SplitFace(face_copy, splitplane);
+    if (frontFragment) {
+        AddMarksurfaces_r(face, frontFragment, node->children[0]);
+    }
+    if (backFragment) {
+        AddMarksurfaces_r(face, backFragment, node->children[1]);
+    }
 }
 
 /*
@@ -529,8 +535,16 @@ void MakeMarkFaces(mapentity_t* entity, node_t* node)
 
     // for the faces on this splitting node..
     for (face_t *face : node->facelist) {
-        // add this face to all descendant leafs (temporary hack)
-        AddMarksurfaces_r(face, node);
+        // add this face to all descendant leafs it touches
+        
+        // make a copy we can clip
+        face_t *face_copy = CopyFace(face);
+
+        if (face->planeside == 0) {
+            AddMarksurfaces_r(face, face_copy, node->children[0]);
+        } else {
+            AddMarksurfaces_r(face, face_copy, node->children[1]);
+        }
     }
 
     // process child nodes recursively
@@ -692,8 +706,7 @@ void MakeVisibleFaces(mapentity_t* entity, node_t* headnode)
             if (!face.visible) {
                 continue;
             }
-            face_t *temp = NewFaceFromFace(&face);
-            temp->w = face.w;
+            face_t *temp = CopyFace(&face);
 
             AddFaceToTree_r(entity, temp, &brush, headnode);
         }
diff --git a/qbsp/test_qbsp.cc b/qbsp/test_qbsp.cc
index 47c7ad70..52a3eca2 100644
--- a/qbsp/test_qbsp.cc
+++ b/qbsp/test_qbsp.cc
@@ -347,7 +347,7 @@ TEST(testmaps_q1, simple_sealed2)
     const qvec3d player_pos{-56, -96, 120};
     const qvec3d other_empty_leaf_pos{-71, -288, 102};
     auto *player_leaf = BSP_FindLeafAtPoint(&bsp, &bsp.dmodels[0], player_pos);
-    auto *other_leaf = BSP_FindLeafAtPoint(&bsp, &bsp.dmodels[0], player_pos);
+    auto *other_leaf = BSP_FindLeafAtPoint(&bsp, &bsp.dmodels[0], other_empty_leaf_pos);
 
     auto player_markfaces = Leaf_Markfaces(&bsp, player_leaf);
     auto other_markfaces = Leaf_Markfaces(&bsp, other_leaf);