diff --git a/src/multibody/model.hxx b/src/multibody/model.hxx
index 8d2066499f31be75ec99566191176ec15e366d13..be4aa1980dfea392d4cef02f9e789289de0a9544 100644
--- a/src/multibody/model.hxx
+++ b/src/multibody/model.hxx
@@ -216,7 +216,7 @@ namespace se3
     computeLastChild(ref);
 
     /* Init for Cholesky */
-    U = Eigen::MatrixXd::Identity(ref.nv,ref.nv);
+    U.setIdentity();
     computeParents_fromRow(ref);
 
     /* Init Jacobian */