diff --git a/gtsam_unstable/dynamics/tests/testSimpleHelicopter.cpp b/gtsam_unstable/dynamics/tests/testSimpleHelicopter.cpp
index a3c622d9b..6f75c264c 100644
--- a/gtsam_unstable/dynamics/tests/testSimpleHelicopter.cpp
+++ b/gtsam_unstable/dynamics/tests/testSimpleHelicopter.cpp
@@ -90,8 +90,7 @@ Vector newtonEuler(const Vector& Vb, const Vector& Fb, const Matrix& Inertia) {
 TEST( DiscreteEulerPoincareHelicopter, evaluateError) {
   Vector Fu = computeFu(gamma2, u2);
   Vector fGravity_g1 = zero(6);
-  Vector subVector = g1.rotation().unrotate(Point3(0.0, 0.0, -mass*9.81));
-  fGravity_g1.segment(3,subVector.size()) = subVector;
+  fGravity_g1.segment<3>(3) = g1.rotation().unrotate(Vector3(0, 0, -mass*9.81));  // gravity force in g1 frame
   Vector Fb = Fu+fGravity_g1;
 
   Vector dV = newtonEuler(V1_g1, Fb, Inertia);