diff --git a/src/BVH/BVH_BinaryTree.lxx b/src/BVH/BVH_BinaryTree.lxx
index 343288ebc7..54a036da80 100644
--- a/src/BVH/BVH_BinaryTree.lxx
+++ b/src/BVH/BVH_BinaryTree.lxx
@@ -293,7 +293,7 @@ BVH_Tree<T, N, BVH_QuadTree>* BVH_Tree<T, N, BVH_BinaryTree>::CollapseToQuadTree
       aNodeInfo = BVH_Vec4i (0 /* inner flag */,
         aNbNodes, aGrandChildNodes.Size() - 1, std::get<1> (aNode) /* level */);
 
-      aQBVH->myDepth = Max (aQBVH->myDepth, std::get<1> (aNode));
+      aQBVH->myDepth = Max (aQBVH->myDepth, std::get<1> (aNode) + 1);
 
       aNbNodes += aGrandChildNodes.Size();
     }