diff --git a/gtsam/nonlinear/Expression.h b/gtsam/nonlinear/Expression.h
index 502579cf7..1c4331de8 100644
--- a/gtsam/nonlinear/Expression.h
+++ b/gtsam/nonlinear/Expression.h
@@ -27,6 +27,7 @@
 #include <boost/bind.hpp>
 #include <boost/range/adaptor/map.hpp>
 #include <boost/range/algorithm.hpp>
+#include <boost/make_shared.hpp>
 
 class ExpressionFactorShallowTest;