diff --git a/gtsam_unstable/nonlinear/Expression-inl.h b/gtsam_unstable/nonlinear/Expression-inl.h
index 5ee1ca272..08a0e0bc6 100644
--- a/gtsam_unstable/nonlinear/Expression-inl.h
+++ b/gtsam_unstable/nonlinear/Expression-inl.h
@@ -392,7 +392,11 @@ class ExpressionNode {
 
 protected:
 
-  ExpressionNode() {
+  size_t traceSize_;
+
+  /// Constructor, traceSize is size of the execution trace of expression rooted here
+  ExpressionNode(size_t traceSize = 0) :
+      traceSize_(traceSize) {
   }
 
 public:
@@ -404,17 +408,17 @@ public:
   /// Return keys that play in this expression as a set
   virtual std::set<Key> keys() const = 0;
 
+  // Return size needed for memory buffer in traceExecution
+  size_t traceSize() const {
+    return traceSize_;
+  }
+
   /// Return value
   virtual T value(const Values& values) const = 0;
 
   /// Return value and derivatives
   virtual Augmented<T> forward(const Values& values) const = 0;
 
-  // Return size needed for memory buffer in traceExecution
-  virtual size_t traceSize() const {
-    return 0;
-  }
-
   /// Construct an execution trace for reverse AD
   virtual T traceExecution(const Values& values, ExecutionTrace<T>& trace,
       char* raw) const = 0;
@@ -519,8 +523,9 @@ private:
   boost::shared_ptr<ExpressionNode<A1> > expressionA1_;
 
   /// Constructor with a unary function f, and input argument e
-  UnaryExpression(Function f, const Expression<A1>& e) :
-      function_(f), expressionA1_(e.root()) {
+  UnaryExpression(Function f, const Expression<A1>& e1) :
+      ExpressionNode<T>(sizeof(Record) + e1.traceSize()), //
+      function_(f), expressionA1_(e1.root()) {
   }
 
   friend class Expression<T> ;
@@ -551,11 +556,6 @@ public:
   typedef boost::mpl::vector<Numbered<A1, 1> > Arguments;
   typedef typename GenerateRecord<T, Arguments>::type Record;
 
-  // Return size needed for memory buffer in traceExecution
-  virtual size_t traceSize() const {
-    return sizeof(Record) + expressionA1_->traceSize();
-  }
-
   /// Construct an execution trace for reverse AD
   virtual T traceExecution(const Values& values, ExecutionTrace<T>& trace,
       char* raw) const {
@@ -592,7 +592,8 @@ private:
   /// Constructor with a binary function f, and two input arguments
   BinaryExpression(Function f, //
       const Expression<A1>& e1, const Expression<A2>& e2) :
-      function_(f), expressionA1_(e1.root()), expressionA2_(e2.root()) {
+      ExpressionNode<T>(sizeof(Record) + e1.traceSize() + e2.traceSize()), function_(
+          f), expressionA1_(e1.root()), expressionA2_(e2.root()) {
   }
 
   friend class Expression<T> ;
@@ -632,12 +633,6 @@ public:
   typedef boost::mpl::vector<Numbered<A1, 1>, Numbered<A2, 2> > Arguments;
   typedef typename GenerateRecord<T, Arguments>::type Record;
 
-  // Return size needed for memory buffer in traceExecution
-  virtual size_t traceSize() const {
-    return sizeof(Record) + expressionA1_->traceSize()
-        + expressionA2_->traceSize();
-  }
-
   /// Construct an execution trace for reverse AD
   /// The raw buffer is [Record | A1 raw | A2 raw]
   virtual T traceExecution(const Values& values, ExecutionTrace<T>& trace,
@@ -682,7 +677,9 @@ private:
       Function f, //
       const Expression<A1>& e1, const Expression<A2>& e2,
       const Expression<A3>& e3) :
-      function_(f), expressionA1_(e1.root()), expressionA2_(e2.root()), expressionA3_(
+      ExpressionNode<T>(
+          sizeof(Record) + e1.traceSize() + e2.traceSize() + e3.traceSize()), function_(
+          f), expressionA1_(e1.root()), expressionA2_(e2.root()), expressionA3_(
           e3.root()) {
   }
 
@@ -729,12 +726,6 @@ public:
   typedef boost::mpl::vector<Numbered<A1, 1>, Numbered<A2, 2>, Numbered<A3, 3> > Arguments;
   typedef typename GenerateRecord<T, Arguments>::type Record;
 
-  // Return size needed for memory buffer in traceExecution
-  virtual size_t traceSize() const {
-    return sizeof(Record) + expressionA1_->traceSize()
-        + expressionA2_->traceSize() + expressionA2_->traceSize();
-  }
-
   /// Construct an execution trace for reverse AD
   virtual T traceExecution(const Values& values, ExecutionTrace<T>& trace,
       char* raw) const {