diff --git a/python/gtsam/preamble/base.h b/python/gtsam/preamble/base.h
index d07a75f6f..b1ed2ba14 100644
--- a/python/gtsam/preamble/base.h
+++ b/python/gtsam/preamble/base.h
@@ -10,3 +10,5 @@
  * Without this they will be automatically converted to a Python object, and all
  * mutations on Python side will not be reflected on C++.
  */
+
+PYBIND11_MAKE_OPAQUE(std::vector<gtsam::Matrix>); // JacobianVector