diff --git a/gtsam/geometry/Cal3_S2Stereo.h b/gtsam/geometry/Cal3_S2Stereo.h
index 18977d409..b22416c37 100644
--- a/gtsam/geometry/Cal3_S2Stereo.h
+++ b/gtsam/geometry/Cal3_S2Stereo.h
@@ -63,6 +63,7 @@ namespace gtsam {
 		void serialize(Archive & ar, const unsigned int version)
 		{
 			ar & BOOST_SERIALIZATION_NVP(b_);
+			ar & BOOST_SERIALIZATION_BASE_OBJECT_NVP(Cal3_S2);
 		}
 	};