diff --git a/python/collision-geometries.cc b/python/collision-geometries.cc
index 14ee334a5ef780786446781feb6c547307f8d225..45c1cf39a9e9cdf3cb58a1ac919a4c9772259a92 100644
--- a/python/collision-geometries.cc
+++ b/python/collision-geometries.cc
@@ -87,7 +87,10 @@ struct BVHModelBaseWrapper {
   }
 
   static RefRowMatrixX3 vertices(BVHModelBase& bvh) {
-    return MapRowMatrixX3((*(bvh.vertices))[0].data(), bvh.num_vertices, 3);
+    if (bvh.num_vertices > 0)
+      return MapRowMatrixX3(bvh.vertices->data()->data(), bvh.num_vertices, 3);
+    else
+      return MapRowMatrixX3(NULL, bvh.num_vertices, 3);
   }
 
   static Triangle tri_indices(const BVHModelBase& bvh, unsigned int i) {