diff --git a/include/dem/particle_particle_contact_force.h b/include/dem/particle_particle_contact_force.h
index 651048f9d2..cd0607521b 100644
--- a/include/dem/particle_particle_contact_force.h
+++ b/include/dem/particle_particle_contact_force.h
@@ -554,7 +554,7 @@ class ParticleParticleContactForce
       (tangential_spring_constant * contact_info.tangential_overlap) +
       damping_tangential_force;
 
-    double coulomb_threshold =
+    const double coulomb_threshold =
       this->effective_coefficient_of_friction[vec_particle_type_index(
         particle_one_type, particle_two_type)] *
       normal_force_value;