diff --git a/src/model/contact_mechanics/contact_element.hh b/src/model/contact_mechanics/contact_element.hh
index b1ba3db3d..040c158df 100644
--- a/src/model/contact_mechanics/contact_element.hh
+++ b/src/model/contact_mechanics/contact_element.hh
@@ -1,86 +1,86 @@
 /**
  * @file   contact_element.hh
  *
  * @author Mohit Pundir <mohit.pundir@epfl.ch>
  *
  * @date creation: Mon Dec 13 2010
  * @date last modification: Tue Jun 08 2021
  *
  * @brief  Mother class for all detection algorithms
  *
  *
  * @section LICENSE
  *
  * Copyright (©) 2010-2021 EPFL (Ecole Polytechnique Fédérale de Lausanne)
  * Laboratory (LSMS - Laboratoire de Simulation en Mécanique des Solides)
  *
  * Akantu is free software: you can redistribute it and/or modify it under the
  * terms of the GNU Lesser General Public License as published by the Free
  * Software Foundation, either version 3 of the License, or (at your option) any
  * later version.
  *
  * Akantu is distributed in the hope that it will be useful, but WITHOUT ANY
  * WARRANTY; without even the implied warranty of MERCHANTABILITY or FITNESS FOR
  * A PARTICULAR PURPOSE. See the GNU Lesser General Public License for more
  * details.
  *
  * You should have received a copy of the GNU Lesser General Public License
  * along with Akantu. If not, see <http://www.gnu.org/licenses/>.
  *
  */
 
 /* -------------------------------------------------------------------------- */
 #include "aka_common.hh"
-
+#include "element.hh"
 /* -------------------------------------------------------------------------- */
 
 #ifndef __AKANTU_CONTACT_ELEMENT_HH__
 #define __AKANTU_CONTACT_ELEMENT_HH__
 
 /* -------------------------------------------------------------------------- */
 
 namespace akantu {
 
 using SlaveType = UInt;
 using MasterType = Element;
 
 class ContactElement {
 
   /* ------------------------------------------------------------------------ */
   /* Constructor/ Destructors                                                 */
   /* ------------------------------------------------------------------------ */
 public:
   ContactElement() = default;
 
   ContactElement(const SlaveType & slave, const MasterType & master)
       : slave(slave), master(master) {}
 
   ~ContactElement() = default;
 
   bool operator==(const ContactElement & other) const {
     return slave == other.slave and master == other.master;
   }
 
   /* ------------------------------------------------------------------------ */
   /* Methods                                                                  */
   /* ------------------------------------------------------------------------ */
 public:
   inline UInt getNbNodes() const {
     auto nb_master_nodes = Mesh::getNbNodesPerElement(master.type);
     return nb_master_nodes + 1;
   }
 
   /* ------------------------------------------------------------------------ */
   /* Class Members                                                            */
   /* ------------------------------------------------------------------------ */
 public:
   /// slave node
   SlaveType slave;
 
   /// master element/node
   MasterType master;
 };
 
 } // namespace akantu
 
 #endif /* __AKANTU_CONTACT_ELEMENT_HH__ */