diff --git a/python/gtsam/preamble.h b/python/gtsam/preamble.h
index b67df2644..9f3032dd0 100644
--- a/python/gtsam/preamble.h
+++ b/python/gtsam/preamble.h
@@ -7,4 +7,5 @@ PYBIND11_MAKE_OPAQUE(std::vector<gtsam::Key>);
 #endif
 PYBIND11_MAKE_OPAQUE(std::vector<gtsam::Point2, Eigen::aligned_allocator<gtsam::Point2> >);
 PYBIND11_MAKE_OPAQUE(std::vector<gtsam::Pose3>);
-PYBIND11_MAKE_OPAQUE(std::vector<gtsam::BetweenFactor<gtsam::Pose3>>);
+PYBIND11_MAKE_OPAQUE(std::vector<boost::shared_ptr<gtsam::BetweenFactor<gtsam::Pose3> > >);
+PYBIND11_MAKE_OPAQUE(std::vector<boost::shared_ptr<gtsam::BetweenFactor<gtsam::Pose2> > >);