diff --git a/gtsam_unstable/nonlinear/Expression-inl.h b/gtsam_unstable/nonlinear/Expression-inl.h
index ef5d62185..f8ad04ba1 100644
--- a/gtsam_unstable/nonlinear/Expression-inl.h
+++ b/gtsam_unstable/nonlinear/Expression-inl.h
@@ -28,16 +28,21 @@ namespace gtsam {
 template<typename T>
 class Expression;
 
+//#define NEW_CLASS
+#ifdef NEW_CLASS
 class JacobianMap: public std::map<Key, Matrix> {
 public:
   void add(Key key, const Matrix& H) {
     iterator it = find(key);
     if (it != end())
-      it->second += H;
+    it->second += H;
     else
-      insert(std::make_pair(key, H));
+    insert(std::make_pair(key, H));
   }
 };
+#else
+typedef std::map<Key, Matrix> JacobianMap;
+#endif
 
 //-----------------------------------------------------------------------------
 /**
@@ -56,13 +61,33 @@ private:
   /// Insert terms into jacobians_, premultiplying by H, adding if already exists
   void add(const JacobianMap& terms) {
     BOOST_FOREACH(const Pair& term, terms)
-      jacobians_.add(term.first, term.second);
+#ifdef NEW_CLASS
+    jacobians_.add(term.first, term.second);
+#else
+    {
+      JacobianMap::iterator it = jacobians_.find(term.first);
+      if (it != jacobians_.end())
+        it->second += term.second;
+      else
+        jacobians_[term.first] = term.second;
+    }
+#endif
   }
 
   /// Insert terms into jacobians_, premultiplying by H, adding if already exists
   void add(const Matrix& H, const JacobianMap& terms) {
     BOOST_FOREACH(const Pair& term, terms)
-      jacobians_.add(term.first, H * term.second);
+#ifdef NEW_CLASS
+    jacobians_.add(term.first, H * term.second);
+#else
+    {
+      JacobianMap::iterator it = jacobians_.find(term.first);
+      if (it != jacobians_.end())
+        it->second += H * term.second;
+      else
+        jacobians_[term.first] = H * term.second;
+    }
+#endif
   }
 
 public:
@@ -275,11 +300,19 @@ public:
     /// If the expression is just a leaf, we just insert an identity matrix
     virtual void reverseAD(JacobianMap& jacobians) const {
       size_t n = T::Dim();
-      jacobians.add(key, Eigen::MatrixXd::Identity(n, n));
+      jacobians[key] = Eigen::MatrixXd::Identity(n, n);
     }
     /// Base case: given df/dT, add it jacobians with correct key and we are done
     virtual void reverseAD(const Matrix& H, JacobianMap& jacobians) const {
+#ifdef NEW_CLASS
       jacobians.add(key, H);
+#else
+      JacobianMap::iterator it = jacobians.find(key);
+      if (it != jacobians.end())
+        it->second += H;
+      else
+        jacobians[key] = H;
+#endif
     }
   };