diff --git a/src/functionObjects/field/externalCoupled/externalCoupledTemperatureMixed/externalCoupledTemperatureMixedFvPatchScalarField.C b/src/functionObjects/field/externalCoupled/externalCoupledTemperatureMixed/externalCoupledTemperatureMixedFvPatchScalarField.C
index 5a06b0dc361ceaf7aa175a05818eef347cb05006..f1d78d5290dc36d01c8170eef0ef7da888536cba 100644
--- a/src/functionObjects/field/externalCoupled/externalCoupledTemperatureMixed/externalCoupledTemperatureMixedFvPatchScalarField.C
+++ b/src/functionObjects/field/externalCoupled/externalCoupledTemperatureMixed/externalCoupledTemperatureMixedFvPatchScalarField.C
@@ -281,7 +281,7 @@ void Foam::externalCoupledTemperatureMixedFvPatchScalarField::writeData
 
 
     // Heat transfer coefficient [W/m2/K]
-    const scalarField htc(qDot/(Twall - Tfluid + 1e-3));
+    const scalarField htc(qDot/(max(Twall - Tfluid), 1e-3));
 
     const Field<scalar>& magSf = this->patch().magSf();