diff --git a/include/mitsuba/core/octree.h b/include/mitsuba/core/octree.h
index 047a074f..fa9f6b85 100644
--- a/include/mitsuba/core/octree.h
+++ b/include/mitsuba/core/octree.h
@@ -140,7 +140,7 @@ public:
 			perm[i] = i;
 
 		/* Build the kd-tree and compute a suitable permutation of the elements */
-		m_root = build(m_aabb, 0, &perm[0], &temp[0], &perm[0], &perm[m_items.size()-1]);
+		m_root = build(m_aabb, 0, &perm[0], &temp[0], &perm[0], &perm[0] + m_items.size());
 
 		/* Apply the permutation */
 		permute_inplace(&m_items[0], perm);