diff --git a/gtsam/navigation/PreintegratedRotation.h b/gtsam/navigation/PreintegratedRotation.h
index 0d68a6e18..71ef5d08f 100644
--- a/gtsam/navigation/PreintegratedRotation.h
+++ b/gtsam/navigation/PreintegratedRotation.h
@@ -35,8 +35,8 @@ struct GTSAM_EXPORT PreintegratedRotationParams {
 
   PreintegratedRotationParams() : gyroscopeCovariance(I_3x3) {}
 
-  PreintegratedRotationParams(Matrix3 gyroscope_covariance,
-                              boost::optional<Vector3> omega_coriolis) 
+  PreintegratedRotationParams(const Matrix3& gyroscope_covariance,
+                              boost::optional<Vector3> omega_coriolis)
     : gyroscopeCovariance(gyroscope_covariance) {
       if (omega_coriolis)
         omegaCoriolis.reset(omega_coriolis.get());