diff --git a/gtsam_unstable/nonlinear/Expression-inl.h b/gtsam_unstable/nonlinear/Expression-inl.h
index 6f78832b9..ba41ab485 100644
--- a/gtsam_unstable/nonlinear/Expression-inl.h
+++ b/gtsam_unstable/nonlinear/Expression-inl.h
@@ -201,7 +201,7 @@ template<class T>
 class ExecutionTrace {
   enum {
     Constant, Leaf, Function
-  } type;
+  } kind;
   union {
     Key key;
     CallRecord<T::dimension>* ptr;
@@ -209,25 +209,25 @@ class ExecutionTrace {
 public:
   /// Pointer always starts out as a Constant
   ExecutionTrace() :
-      type(Constant) {
+      kind(Constant) {
   }
   /// Change pointer to a Leaf Record
   void setLeaf(Key key) {
-    type = Leaf;
+    kind = Leaf;
     content.key = key;
   }
   /// Take ownership of pointer to a Function Record
   void setFunction(CallRecord<T::dimension>* record) {
-    type = Function;
+    kind = Function;
     content.ptr = record;
   }
   /// Print
   void print(const std::string& indent = "") const {
-    if (type == Constant)
+    if (kind == Constant)
       std::cout << indent << "Constant" << std::endl;
-    else if (type == Leaf)
+    else if (kind == Leaf)
       std::cout << indent << "Leaf, key = " << content.key << std::endl;
-    else if (type == Function) {
+    else if (kind == Function) {
       std::cout << indent << "Function" << std::endl;
       content.ptr->print(indent + "  ");
     }
@@ -235,7 +235,7 @@ public:
   /// Return record pointer, quite unsafe, used only for testing
   template<class Record>
   boost::optional<Record*> record() {
-    if (type != Function)
+    if (kind != Function)
       return boost::none;
     else {
       Record* p = dynamic_cast<Record*>(content.ptr);
@@ -245,38 +245,41 @@ public:
   // *** This is the main entry point for reverseAD, called from Expression::augmented ***
   // Called only once, either inserts identity into Jacobians (Leaf) or starts AD (Function)
   void startReverseAD(JacobianMap& jacobians) const {
-    if (type == Leaf) {
+    if (kind == Leaf) {
       // This branch will only be called on trivial Leaf expressions, i.e. Priors
       size_t n = T::Dim();
       jacobians[content.key] = Eigen::MatrixXd::Identity(n, n);
-    } else if (type == Function)
+    } else if (kind == Function)
       // This is the more typical entry point, starting the AD pipeline
       // It is inside the startReverseAD that the correctly dimensioned pipeline is chosen.
       content.ptr->startReverseAD(jacobians);
   }
   // Either add to Jacobians (Leaf) or propagate (Function)
   void reverseAD(const Matrix& dTdA, JacobianMap& jacobians) const {
-    if (type == Leaf) {
+    if (kind == Leaf) {
       JacobianMap::iterator it = jacobians.find(content.key);
       if (it != jacobians.end())
         it->second += dTdA;
       else
         jacobians[content.key] = dTdA;
-    } else if (type == Function)
+    } else if (kind == Function)
       content.ptr->reverseAD(dTdA, jacobians);
   }
   // Either add to Jacobians (Leaf) or propagate (Function)
   typedef Eigen::Matrix<double, 2, T::dimension> Jacobian2T;
   void reverseAD2(const Jacobian2T& dTdA, JacobianMap& jacobians) const {
-    if (type == Leaf) {
+    if (kind == Leaf) {
       JacobianMap::iterator it = jacobians.find(content.key);
       if (it != jacobians.end())
         it->second += dTdA;
       else
         jacobians[content.key] = dTdA;
-    } else if (type == Function)
+    } else if (kind == Function)
       content.ptr->reverseAD2(dTdA, jacobians);
   }
+
+  /// Define type so we can apply it as a meta-function
+  typedef ExecutionTrace<T> type;
 };
 
 /// Primary template calls the generic Matrix reverseAD pipeline
diff --git a/gtsam_unstable/nonlinear/Expression.h b/gtsam_unstable/nonlinear/Expression.h
index 502826f61..6b28667a7 100644
--- a/gtsam_unstable/nonlinear/Expression.h
+++ b/gtsam_unstable/nonlinear/Expression.h
@@ -147,6 +147,8 @@ public:
     return root_;
   }
 
+  /// Define type so we can apply it as a meta-function
+  typedef Expression<T> type;
 };
 
 // http://stackoverflow.com/questions/16260445/boost-bind-to-operator
diff --git a/gtsam_unstable/nonlinear/tests/testExpressionFactor.cpp b/gtsam_unstable/nonlinear/tests/testExpressionFactor.cpp
index 8e57e7400..04ade90be 100644
--- a/gtsam_unstable/nonlinear/tests/testExpressionFactor.cpp
+++ b/gtsam_unstable/nonlinear/tests/testExpressionFactor.cpp
@@ -429,13 +429,35 @@ TEST(ExpressionFactor, composeTernary) {
 namespace mpl = boost::mpl;
 
 #include <boost/mpl/assert.hpp>
+#include <boost/mpl/transform.hpp>
+#include <boost/mpl/equal.hpp>
 template<class T> struct Incomplete;
 
-typedef mpl::vector<Pose3, Point3, Cal3_S2> MyTypes;
+// Check generation of FunctionalNode
+typedef mpl::vector<Pose3, Point3> MyTypes;
 typedef FunctionalNode<Point2, MyTypes>::type Generated;
 //Incomplete<Generated> incomplete;
 BOOST_MPL_ASSERT((boost::is_same< Matrix2, Generated::Record::Jacobian2T >));
 
+// Try generating vectors of ExecutionTrace
+typedef mpl::vector<ExecutionTrace<Pose3>, ExecutionTrace<Point3> > ExpectedTraces;
+
+typedef mpl::transform<MyTypes,ExecutionTrace<MPL::_1> >::type MyTraces;
+BOOST_MPL_ASSERT((boost::mpl::equal< ExpectedTraces, MyTraces >));
+
+template <class T>
+struct MakeTrace {
+  typedef ExecutionTrace<T> type;
+};
+typedef mpl::transform<MyTypes,MakeTrace<MPL::_1> >::type MyTraces1;
+BOOST_MPL_ASSERT((boost::mpl::equal< ExpectedTraces, MyTraces1 >));
+
+// Try generating vectors of Expression types
+typedef mpl::vector<Expression<Pose3>, Expression<Point3> > ExpectedExpressions;
+
+typedef mpl::transform<MyTypes,Expression<MPL::_1> >::type Expressions;
+BOOST_MPL_ASSERT((boost::mpl::equal< ExpectedExpressions, Expressions >));
+
 /* ************************************************************************* */
 int main() {
   TestResult tr;