diff --git a/cpp/BayesNet-inl.h b/cpp/BayesNet-inl.h
index cb74f37f4..c9aeb0e06 100644
--- a/cpp/BayesNet-inl.h
+++ b/cpp/BayesNet-inl.h
@@ -14,6 +14,7 @@ using namespace boost::assign;
 #include "Ordering.h"
 #include "BayesNet.h"
 #include "FactorGraph-inl.h"
+#include "Conditional.h"
 
 using namespace std;
 
diff --git a/cpp/Conditional.h b/cpp/Conditional.h
index 4c955080b..55812f4cb 100644
--- a/cpp/Conditional.h
+++ b/cpp/Conditional.h
@@ -11,6 +11,7 @@
 #include <boost/utility.hpp> // for noncopyable
 #include <boost/serialization/string.hpp>
 #include <boost/serialization/access.hpp>
+#include <boost/serialization/nvp.hpp>
 #include "Testable.h"
 
 namespace gtsam {