diff --git a/gtsam/nonlinear/Expression-inl.h b/gtsam/nonlinear/Expression-inl.h
index 08dd18ee3..a87d9896e 100644
--- a/gtsam/nonlinear/Expression-inl.h
+++ b/gtsam/nonlinear/Expression-inl.h
@@ -455,9 +455,7 @@ struct Jacobian {
 /// meta-function to generate JacobianTA optional reference
 template<class T, class A>
 struct OptionalJacobian {
-  typedef Eigen::Matrix<double, traits::dimension<T>::value,
-      traits::dimension<A>::value> Jacobian;
-  typedef boost::optional<Jacobian&> type;
+  typedef FixedRef<traits::dimension<T>::value, traits::dimension<A>::value> type;
 };
 
 /**
diff --git a/gtsam/nonlinear/Expression.h b/gtsam/nonlinear/Expression.h
index d44d21cd7..940ad1778 100644
--- a/gtsam/nonlinear/Expression.h
+++ b/gtsam/nonlinear/Expression.h
@@ -224,9 +224,8 @@ template<class T>
 struct apply_compose {
   typedef T result_type;
   static const int Dim = traits::dimension<T>::value;
-  typedef Eigen::Matrix<double, Dim, Dim> Jacobian;
-  T operator()(const T& x, const T& y, boost::optional<Jacobian&> H1,
-      boost::optional<Jacobian&> H2) const {
+  T operator()(const T& x, const T& y, FixedRef<Dim, Dim> H1 = boost::none,
+      FixedRef<Dim, Dim> H2 = boost::none) const {
     return x.compose(y, H1, H2);
   }
 };