diff --git a/OdeWorld.h b/OdeWorld.h
index c7fbb85..23eff2a 100644
--- a/OdeWorld.h
+++ b/OdeWorld.h
@@ -63,6 +63,11 @@ class OdeWorld
                         dBodySetGravityMode(m_body, enabled);
                     }
                 }
+                void setUserData(void * user_data)
+                {
+                    m_user_data = user_data;
+                }
+                void * getUserData() { return m_user_data; }
 
             protected:
                 bool    m_is_static;
@@ -75,6 +80,7 @@ class OdeWorld
                 dReal   m_position[3];
                 dReal   m_rotation[12];
                 OdeWorld * m_ode_world;
+                void *  m_user_data;
 
                 void setupGeom(dGeomID geom, dMass * mass,
                         float locx, float locy, float locz,