diff --git a/src/mapnik_map.cpp b/src/mapnik_map.cpp
index 55a48ae638..8ed0af1346 100644
--- a/src/mapnik_map.cpp
+++ b/src/mapnik_map.cpp
@@ -1941,6 +1941,7 @@ void Map::EIO_RenderVectorTile(uv_work_t* req)
                           closure->image_format,
                           closure->scaling_method);
         ren.set_simplify_distance(closure->simplify_distance);
+        ren.set_multi_polygon_union(true);
         ren.apply(closure->scale_denominator);
         std::string new_message;
         if (!tiledata.SerializeToString(&new_message))
diff --git a/src/mapnik_vector_tile.cpp b/src/mapnik_vector_tile.cpp
index 5cb67d1467..75af08d5d8 100644
--- a/src/mapnik_vector_tile.cpp
+++ b/src/mapnik_vector_tile.cpp
@@ -2656,6 +2656,7 @@ NAN_METHOD(VectorTile::addGeoJSON)
                           area_threshold,
                           strictly_simple);
         ren.set_simplify_distance(simplify_distance);
+        ren.set_multi_polygon_union(true);
         ren.apply();
         detail::add_tile(d->buffer_,tiledata);
         info.GetReturnValue().Set(Nan::True());