diff --git a/src/thermophysicalModels/specie/thermo/thermo/thermoI.H b/src/thermophysicalModels/specie/thermo/thermo/thermoI.H
index 2617da968c..9b8eb30777 100644
--- a/src/thermophysicalModels/specie/thermo/thermo/thermoI.H
+++ b/src/thermophysicalModels/specie/thermo/thermo/thermoI.H
@@ -281,7 +281,7 @@ template<class Thermo, template<class> class Type>
 inline Foam::scalar
 Foam::species::thermo<Thermo, Type>::K(const scalar p, const scalar T) const
 {
-    scalar arg = -this->nMoles()*this->g(p, T)/(RR*T);
+    scalar arg = -this->nMoles()*this->g(Pstd, T)/(RR*T);
 
     if (arg < 600.0)
     {