diff --git a/gtsam/geometry/CalibratedCamera.cpp b/gtsam/geometry/CalibratedCamera.cpp
index f0c70408e..a45da9789 100644
--- a/gtsam/geometry/CalibratedCamera.cpp
+++ b/gtsam/geometry/CalibratedCamera.cpp
@@ -61,6 +61,8 @@ Point2 CalibratedCamera::project(const Point3& point,
 	const Rot3& R = pose.rotation();
 	const Point3& r1 = R.r1(), r2 = R.r2(), r3 = R.r3();
 	Point3 q = pose.transform_to(point);
+	if(q.z() <= 0)
+	  throw CheiralityException();
 
 	if (D_intrinsic_pose || D_intrinsic_point) {
 		double X = q.x(), Y = q.y(), Z = q.z();
diff --git a/gtsam/geometry/CalibratedCamera.h b/gtsam/geometry/CalibratedCamera.h
index 880bb9316..4538b3367 100644
--- a/gtsam/geometry/CalibratedCamera.h
+++ b/gtsam/geometry/CalibratedCamera.h
@@ -23,6 +23,11 @@
 
 namespace gtsam {
 
+  class CheiralityException: public std::runtime_error {
+  public:
+    CheiralityException() : std::runtime_error("Cheirality Exception") {}
+  };
+
 	/**
 	 * A Calibrated camera class [R|-R't], calibration K=I.
 	 * If calibration is known, it is more computationally efficient
diff --git a/gtsam/slam/ProjectionFactor.h b/gtsam/slam/ProjectionFactor.h
index ee5649f78..6940e367f 100644
--- a/gtsam/slam/ProjectionFactor.h
+++ b/gtsam/slam/ProjectionFactor.h
@@ -82,9 +82,18 @@ namespace gtsam {
 		/// Evaluate error h(x)-z and optionally derivatives
 		Vector evaluateError(const Pose3& pose, const Point3& point,
 				boost::optional<Matrix&> H1, boost::optional<Matrix&> H2) const {
-			SimpleCamera camera(*K_, pose);
-			Point2 reprojectionError(camera.project(point, H1, H2) - z_);
-			return reprojectionError.vector();
+			try {
+	      SimpleCamera camera(*K_, pose);
+			  Point2 reprojectionError(camera.project(point, H1, H2) - z_);
+	      return reprojectionError.vector();
+			}
+			catch( CheiralityException& e) {
+			  if (H1) *H1 = zeros(2,6);
+			  if (H2) *H2 = zeros(2,3);
+			  cout << e.what() << ": Landmark "<< this->key2_.index() <<
+			      " moved behind camera " << this->key1_.index() << endl;
+			  return zero(2);
+			}
 		}
 
     /** return the measurement */