diff --git a/gtsam_unstable/nonlinear/ExpressionFactor.h b/gtsam_unstable/nonlinear/ExpressionFactor.h
index 69056e6ef..f7b61120a 100644
--- a/gtsam_unstable/nonlinear/ExpressionFactor.h
+++ b/gtsam_unstable/nonlinear/ExpressionFactor.h
@@ -108,7 +108,7 @@ public:
   virtual boost::shared_ptr<GaussianFactor> linearize(const Values& x) const {
 
     // Only linearize if the factor is active
-    if (!this->active(x))
+    if (!active(x))
       return boost::shared_ptr<JacobianFactor>();
 
     // Create a writeable JacobianFactor in advance
@@ -128,11 +128,13 @@ public:
 
     // Evaluate error to get Jacobians and RHS vector b
     T value = expression_.value(x, map); // <<< Reverse AD happens here !
-    Ab(size()).col(0) = -measurement_.localCoordinates(value);
+    Vector b(-measurement_.localCoordinates(value));
 
-    // Whiten the corresponding system now
-    // TODO ! this->noiseModel_->WhitenSystem(Ab);
+    // Whiten the corresponding system
+    // Note the Ab.matrix() includes uninitialized RHS, but this beats taking it apart
+    noiseModel_->WhitenSystem(Ab.matrix(),b);
 
+    Ab(size()).col(0) = b;
     return factor;
   }
 };
diff --git a/gtsam_unstable/nonlinear/tests/testExpressionFactor.cpp b/gtsam_unstable/nonlinear/tests/testExpressionFactor.cpp
index 23c2fa1ce..fa2e5cadb 100644
--- a/gtsam_unstable/nonlinear/tests/testExpressionFactor.cpp
+++ b/gtsam_unstable/nonlinear/tests/testExpressionFactor.cpp
@@ -65,41 +65,41 @@ TEST(ExpressionFactor, Leaf) {
   EXPECT( assert_equal(*old.linearize(values), *gf2, 1e-9));
 }
 
-///* ************************************************************************* */
-//// non-zero noise model
-//TEST(ExpressionFactor, Model) {
-//  using namespace leaf;
-//
-//  SharedNoiseModel model = noiseModel::Diagonal::Sigmas(Vector2(0.1, 0.01));
-//
-//  // Create old-style factor to create expected value and derivatives
-//  PriorFactor<Point2> old(2, Point2(0, 0), model);
-//
-//  // Concise version
-//  ExpressionFactor<Point2> f(model, Point2(0, 0), p);
-//  EXPECT_DOUBLES_EQUAL(old.error(values), f.error(values), 1e-9);
-//  EXPECT_LONGS_EQUAL(2, f.dim());
-//  boost::shared_ptr<GaussianFactor> gf2 = f.linearize(values);
-//  EXPECT( assert_equal(*old.linearize(values), *gf2, 1e-9));
-//}
-//
-///* ************************************************************************* */
-//// Constrained noise model
-//TEST(ExpressionFactor, Constrained) {
-//  using namespace leaf;
-//
-//  SharedDiagonal model = noiseModel::Constrained::MixedSigmas(Vector2(0.2, 0));
-//
-//  // Create old-style factor to create expected value and derivatives
-//  PriorFactor<Point2> old(2, Point2(0, 0), model);
-//
-//  // Concise version
-//  ExpressionFactor<Point2> f(model, Point2(0, 0), p);
-//  EXPECT_DOUBLES_EQUAL(old.error(values), f.error(values), 1e-9);
-//  EXPECT_LONGS_EQUAL(2, f.dim());
-//  boost::shared_ptr<GaussianFactor> gf2 = f.linearize(values);
-//  EXPECT( assert_equal(*old.linearize(values), *gf2, 1e-9));
-//}
+/* ************************************************************************* */
+// non-zero noise model
+TEST(ExpressionFactor, Model) {
+  using namespace leaf;
+
+  SharedNoiseModel model = noiseModel::Diagonal::Sigmas(Vector2(0.1, 0.01));
+
+  // Create old-style factor to create expected value and derivatives
+  PriorFactor<Point2> old(2, Point2(0, 0), model);
+
+  // Concise version
+  ExpressionFactor<Point2> f(model, Point2(0, 0), p);
+  EXPECT_DOUBLES_EQUAL(old.error(values), f.error(values), 1e-9);
+  EXPECT_LONGS_EQUAL(2, f.dim());
+  boost::shared_ptr<GaussianFactor> gf2 = f.linearize(values);
+  EXPECT( assert_equal(*old.linearize(values), *gf2, 1e-9));
+}
+
+/* ************************************************************************* */
+// Constrained noise model
+TEST(ExpressionFactor, Constrained) {
+  using namespace leaf;
+
+  SharedDiagonal model = noiseModel::Constrained::MixedSigmas(Vector2(0.2, 0));
+
+  // Create old-style factor to create expected value and derivatives
+  PriorFactor<Point2> old(2, Point2(0, 0), model);
+
+  // Concise version
+  ExpressionFactor<Point2> f(model, Point2(0, 0), p);
+  EXPECT_DOUBLES_EQUAL(old.error(values), f.error(values), 1e-9);
+  EXPECT_LONGS_EQUAL(2, f.dim());
+  boost::shared_ptr<GaussianFactor> gf2 = f.linearize(values);
+  EXPECT( assert_equal(*old.linearize(values), *gf2, 1e-9));
+}
 
 /* ************************************************************************* */
 // Unary(Leaf))