diff --git a/y2020/control_loops/drivetrain/localizer.cc b/y2020/control_loops/drivetrain/localizer.cc
index 5169a64..906bb4b 100644
--- a/y2020/control_loops/drivetrain/localizer.cc
+++ b/y2020/control_loops/drivetrain/localizer.cc
@@ -28,8 +28,7 @@
 
 // Calculates the pose implied by the camera target, just based on
 // distance/heading components.
-Eigen::Vector3f CalculateImpliedPose(const Localizer::State &X,
-                                     const Eigen::Matrix4f &H_field_target,
+Eigen::Vector3f CalculateImpliedPose(const Eigen::Matrix4f &H_field_target,
                                      const Localizer::Pose &pose_robot_target) {
   // This code overrides the pose sent directly from the camera code and
   // effectively distills it down to just a distance + heading estimate, on
@@ -47,8 +46,12 @@
   // an accurate distance + heading to the goal.
 
   // Calculate the heading to the robot in the target's coordinate frame.
+  // Reminder on what the numbers mean:
+  // rel_theta: The orientation of the target in the robot frame.
+  // heading: heading from the robot to the target in the robot frame. I.e.,
+  //   atan2(y, x) for x/y of the target in the robot frame.
   const float implied_heading_from_target = aos::math::NormalizeAngle(
-      pose_robot_target.heading() + M_PI + X(Localizer::StateIdx::kTheta));
+      M_PI - pose_robot_target.rel_theta() + pose_robot_target.heading());
   const float implied_distance = pose_robot_target.xy_norm();
   const Eigen::Vector4f robot_pose_in_target_frame(
       implied_distance * std::cos(implied_heading_from_target),
@@ -302,8 +305,8 @@
         Eigen::Vector3f::Zero(), &U, {},
         [H, H_field_target, pose_robot_target, state_at_capture](
             const State &, const Input &) -> Eigen::Vector3f {
-          const Eigen::Vector3f Z = CalculateImpliedPose(
-              state_at_capture.value(), H_field_target, pose_robot_target);
+          const Eigen::Vector3f Z =
+              CalculateImpliedPose(H_field_target, pose_robot_target);
           // Just in case we ever do encounter any, drop measurements if they
           // have non-finite numbers.
           if (!Z.allFinite()) {
diff --git a/y2020/control_loops/drivetrain/localizer_test.cc b/y2020/control_loops/drivetrain/localizer_test.cc
index a1b6121..c0da838 100644
--- a/y2020/control_loops/drivetrain/localizer_test.cc
+++ b/y2020/control_loops/drivetrain/localizer_test.cc
@@ -84,6 +84,9 @@
   H.block<3, 1>(0, 3) << 10.0, 0, 0;
   locations.push_back(H);
   H.block<3, 1>(0, 3) << -10.0, 0, 0;
+  H.block<3, 3>(0, 0) =
+      Eigen::AngleAxis<double>(1.1, Eigen::Vector3d::UnitZ()) *
+      H.block<3, 3>(0, 0);
   locations.push_back(H);
   return locations;
 }