diff --git a/src/thermophysicalModels/specie/transport/cantera/canteraTransport.C b/src/thermophysicalModels/specie/transport/cantera/canteraTransport.C
index 8747bc0a..e771ea24 100644
--- a/src/thermophysicalModels/specie/transport/cantera/canteraTransport.C
+++ b/src/thermophysicalModels/specie/transport/cantera/canteraTransport.C
@@ -159,12 +159,14 @@ void Foam::canteraTransport<Thermo>::calculateDiffusivities
 {
     cm_.gas()->setState_TPX(T, p, X_.cdata());
 
+    const scalar relTol = 1.0e-15;
+
     // check for singular case (Xi = 1)
     label idxFracOne = -1;
     scalar sumX = sum(X_);
     forAll (X_, i)
     {
-        if (X_[i]/sumX == 1.0)
+        if ((sumX-X_[i])/sumX < relTol)
         {
             idxFracOne = i;
             break;