diff --git a/opm/material/constraintsolvers/ChiFlash.hpp b/opm/material/constraintsolvers/ChiFlash.hpp
index 8cc954537..77d691cd6 100644
--- a/opm/material/constraintsolvers/ChiFlash.hpp
+++ b/opm/material/constraintsolvers/ChiFlash.hpp
@@ -931,8 +931,11 @@ protected:
 
             {
                 // (f_liquid/f_vapor) - 1 = 0
-                auto local_res = (fluid_state.fugacity(oilPhaseIdx, compIdx) /
-                                  fluid_state.fugacity(gasPhaseIdx, compIdx)) - 1.0;
+                /* auto local_res = (fluid_state.fugacity(oilPhaseIdx, compIdx) /
+                                  fluid_state.fugacity(gasPhaseIdx, compIdx)) - 1.0; */
+                // TODO: it looks this formulation converges quicker while begin with bigger residual
+                auto local_res = (fluid_state.fugacity(oilPhaseIdx, compIdx) -
+                                  fluid_state.fugacity(gasPhaseIdx, compIdx));
                 res[compIdx + numComponents] = Opm::getValue(local_res);
                 for (unsigned i = 0; i < num_equation; ++i) {
                     jac[compIdx + numComponents][i] = local_res.derivative(i);
diff --git a/opm/material/fluidsystems/chifluid/juliathreecomponentfluidsystem.hh b/opm/material/fluidsystems/chifluid/juliathreecomponentfluidsystem.hh
index 32b625972..fd9a04474 100644
--- a/opm/material/fluidsystems/chifluid/juliathreecomponentfluidsystem.hh
+++ b/opm/material/fluidsystems/chifluid/juliathreecomponentfluidsystem.hh
@@ -158,6 +158,8 @@ namespace Opm {
             assert(0 <= phaseIdx && phaseIdx < numPhases);
             assert(0 <= compIdx && compIdx < numComponents);
 
+            // TODO: here the derivatives for the phi are dropped. Should we keep the derivatives against the pressure
+            // and temperature?
             Scalar phi = Opm::getValue(
                     PengRobinsonMixture::computeFugacityCoefficient(fluidState, paramCache, phaseIdx, compIdx));
             return phi;