diff --git a/y2015/control_loops/drivetrain/drivetrain.cc b/y2015/control_loops/drivetrain/drivetrain.cc
index 22a5d48..9ed927a 100644
--- a/y2015/control_loops/drivetrain/drivetrain.cc
+++ b/y2015/control_loops/drivetrain/drivetrain.cc
@@ -192,7 +192,7 @@
         loop_->mutable_U().setZero();
         loop_->mutable_U_uncapped().setZero();
       }
-      loop_->UpdateObserver();
+      loop_->UpdateObserver(loop_->U());
     }
     ::Eigen::Matrix<double, 4, 1> E = loop_->R() - loop_->X_hat();
     LOG_MATRIX(DEBUG, "E", E);