diff --git a/gtsam_unstable/nonlinear/Expression-inl.h b/gtsam_unstable/nonlinear/Expression-inl.h
index d5c5f1279..43d3071ce 100644
--- a/gtsam_unstable/nonlinear/Expression-inl.h
+++ b/gtsam_unstable/nonlinear/Expression-inl.h
@@ -48,7 +48,8 @@ namespace gtsam {
 template<typename T>
 class Expression;
 
-typedef std::map<Key, Eigen::Block<Matrix> > JacobianMap;
+//typedef std::map<Key, Eigen::Block<Matrix> > JacobianMap;
+typedef std::vector<std::pair<Key, Eigen::Block<Matrix> > > JacobianMap;
 
 //-----------------------------------------------------------------------------
 /**
@@ -78,16 +79,28 @@ struct CallRecord {
 template<int ROWS, int COLS>
 void handleLeafCase(const Eigen::Matrix<double, ROWS, COLS>& dTdA,
     JacobianMap& jacobians, Key key) {
-  JacobianMap::iterator it = jacobians.find(key);
-  it->second.block<ROWS, COLS>(0, 0) += dTdA; // block makes HUGE difference
+  for(JacobianMap::iterator it = jacobians.begin(); it != jacobians.end(); ++it)
+  {
+    if((*it).first == key)
+    {
+      (*it).second.block<ROWS, COLS>(0, 0) += dTdA; // block makes HUGE difference
+      break;
+    }
+  }
 }
 /// Handle Leaf Case for Dynamic Matrix type (slower)
 template<>
 void handleLeafCase(
     const Eigen::Matrix<double, Eigen::Dynamic, Eigen::Dynamic>& dTdA,
     JacobianMap& jacobians, Key key) {
-  JacobianMap::iterator it = jacobians.find(key);
-  it->second += dTdA;
+  for(JacobianMap::iterator it = jacobians.begin(); it != jacobians.end(); ++it)
+  {
+    if((*it).first == key)
+    {
+      (*it).second += dTdA; // block makes HUGE difference
+      break;
+    }
+  }
 }
 
 //-----------------------------------------------------------------------------
diff --git a/gtsam_unstable/nonlinear/ExpressionFactor.h b/gtsam_unstable/nonlinear/ExpressionFactor.h
index 84456c934..c9f3fae86 100644
--- a/gtsam_unstable/nonlinear/ExpressionFactor.h
+++ b/gtsam_unstable/nonlinear/ExpressionFactor.h
@@ -87,12 +87,13 @@ public:
 
       // Create and zero out blocks to be passed to expression_
       JacobianMap blocks;
+      blocks.reserve(size());
       for (DenseIndex i = 0; i < size(); i++) {
         Matrix& Hi = H->at(i);
         Hi.resize(Dim, dimensions_[i]);
         Hi.setZero(); // zero out
         Eigen::Block<Matrix> block = Hi.block(0, 0, Dim, dimensions_[i]);
-        blocks.insert(std::make_pair(keys_[i], block));
+        blocks.push_back(std::make_pair(keys_[i], block));
       }
 
       T value = expression_.value(x, blocks);
@@ -121,8 +122,9 @@ public:
 
     // Create blocks into Ab_ to be passed to expression_
     JacobianMap blocks;
+    blocks.reserve(size());
     for (DenseIndex i = 0; i < size(); i++)
-      blocks.insert(std::make_pair(keys_[i], Ab(i)));
+      blocks.push_back(std::make_pair(keys_[i], Ab(i)));
 
     // Evaluate error to get Jacobians and RHS vector b
     T value = expression_.value(x, blocks); // <<< Reverse AD happens here !