diff --git a/src/oneD/StFlow.cpp b/src/oneD/StFlow.cpp
index 161a44612..78a5860cd 100644
--- a/src/oneD/StFlow.cpp
+++ b/src/oneD/StFlow.cpp
@@ -979,7 +979,8 @@ void StFlow::updateDiffFluxes(const doublereal* x, size_t j0, size_t j1)
 
     if (m_do_soret) {
         for (m = j0; m < j1; m++) {
-            gradlogT = 2.0*(T(x,m+1) - T(x,m))/(T(x,m+1) + T(x,m));
+            gradlogT = 2.0 * (T(x,m+1) - T(x,m)) /
+                ((T(x,m+1) + T(x,m)) * (z(m+1) - z(m)));
             for (k = 0; k < m_nsp; k++) {
                 m_flux(k,m) -= m_dthermal(k,m)*gradlogT;
             }