diff --git a/src/combustionModels/singleStepCombustion/singleStepCombustion.C b/src/combustionModels/singleStepCombustion/singleStepCombustion.C
index e09b8363f6..319e5476b2 100644
--- a/src/combustionModels/singleStepCombustion/singleStepCombustion.C
+++ b/src/combustionModels/singleStepCombustion/singleStepCombustion.C
@@ -80,17 +80,12 @@ singleStepCombustion<CombThermoType, ThermoType>::R
 {
     const label specieI = this->thermo_->composition().species()[Y.name()];
 
-    const label fNorm = singleMixture_.specieProd()[specieI];
-
-    const volScalarField fres(singleMixture_.fres(specieI));
-
     const volScalarField wSpecie
     (
         wFuel_*singleMixture_.specieStoichCoeffs()[specieI]
-      / max(fNorm*(Y - fres), scalar(0.001))
     );
 
-    return -fNorm*wSpecie*fres + fNorm*fvm::Sp(wSpecie, Y);
+    return wSpecie + fvm::Sp(0.0*wSpecie, Y);
 }
 
 
diff --git a/tutorials/combustion/fireFoam/les/smallPoolFire2D/constant/combustionProperties b/tutorials/combustion/fireFoam/les/smallPoolFire2D/constant/combustionProperties
index 289df92fcc..619c448058 100644
--- a/tutorials/combustion/fireFoam/les/smallPoolFire2D/constant/combustionProperties
+++ b/tutorials/combustion/fireFoam/les/smallPoolFire2D/constant/combustionProperties
@@ -15,8 +15,8 @@ FoamFile
 }
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
-//combustionModel  infinitelyFastChemistry<psiCombustionModel,gasThermoPhysics>;
-combustionModel  FSD<psiCombustionModel,gasThermoPhysics>;
+combustionModel  infinitelyFastChemistry<psiCombustionModel,gasThermoPhysics>;
+//combustionModel  FSD<psiCombustionModel,gasThermoPhysics>;
 
 active  true;