diff --git a/gtsam/linear/LossFunctions.h b/gtsam/linear/LossFunctions.h
index 4705721a0..4e6a2b609 100644
--- a/gtsam/linear/LossFunctions.h
+++ b/gtsam/linear/LossFunctions.h
@@ -28,6 +28,7 @@
 #include <boost/serialization/optional.hpp>
 #include <boost/serialization/shared_ptr.hpp>
 #include <boost/serialization/singleton.hpp>
+#include <boost/serialization/version.hpp>
 
 namespace gtsam {
 namespace noiseModel {
diff --git a/gtsam/linear/SubgraphBuilder.h b/gtsam/linear/SubgraphBuilder.h
index 5247ea2a2..88c771ba5 100644
--- a/gtsam/linear/SubgraphBuilder.h
+++ b/gtsam/linear/SubgraphBuilder.h
@@ -23,6 +23,7 @@
 
 #include <boost/serialization/nvp.hpp>
 #include <boost/shared_ptr.hpp>
+#include <boost/serialization/version.hpp>
 
 #include <vector>