diff --git a/src/thermophysicalModels/basic/rhoThermo/heRhoThermo.C b/src/thermophysicalModels/basic/rhoThermo/heRhoThermo.C
index 6611218c30..9faeed3de4 100644
--- a/src/thermophysicalModels/basic/rhoThermo/heRhoThermo.C
+++ b/src/thermophysicalModels/basic/rhoThermo/heRhoThermo.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2016 OpenFOAM Foundation
-    Copyright (C) 2015-2017 OpenCFD Ltd.
+    Copyright (C) 2015-2020 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -74,6 +74,9 @@ void Foam::heRhoThermo<BasicPsiThermo, MixtureType>::calculate
         const typename MixtureType::thermoType& mixture_ =
             this->cellMixture(celli);
 
+        const typename MixtureType::thermoType& volMixture_ =
+            this->cellVolMixture(pCells[celli], TCells[celli], celli);
+
         if (this->updateT())
         {
             TCells[celli] = mixture_.THE
@@ -85,7 +88,7 @@ void Foam::heRhoThermo<BasicPsiThermo, MixtureType>::calculate
         }
 
         psiCells[celli] = mixture_.psi(pCells[celli], TCells[celli]);
-        rhoCells[celli] = mixture_.rho(pCells[celli], TCells[celli]);
+        rhoCells[celli] = volMixture_.rho(pCells[celli], TCells[celli]);
 
         muCells[celli] = mixture_.mu(pCells[celli], TCells[celli]);
         alphaCells[celli] = mixture_.alphah(pCells[celli], TCells[celli]);
@@ -116,10 +119,19 @@ void Foam::heRhoThermo<BasicPsiThermo, MixtureType>::calculate
                 const typename MixtureType::thermoType& mixture_ =
                     this->patchFaceMixture(patchi, facei);
 
+                const typename MixtureType::thermoType& volMixture_ =
+                    this->patchFaceVolMixture
+                    (
+                        pp[facei],
+                        pT[facei],
+                        patchi,
+                        facei
+                    );
+
                 phe[facei] = mixture_.HE(pp[facei], pT[facei]);
 
                 ppsi[facei] = mixture_.psi(pp[facei], pT[facei]);
-                prho[facei] = mixture_.rho(pp[facei], pT[facei]);
+                prho[facei] = volMixture_.rho(pp[facei], pT[facei]);
                 pmu[facei] = mixture_.mu(pp[facei], pT[facei]);
                 palpha[facei] = mixture_.alphah(pp[facei], pT[facei]);
             }
@@ -131,13 +143,22 @@ void Foam::heRhoThermo<BasicPsiThermo, MixtureType>::calculate
                 const typename MixtureType::thermoType& mixture_ =
                     this->patchFaceMixture(patchi, facei);
 
+                const typename MixtureType::thermoType& volMixture_ =
+                    this->patchFaceVolMixture
+                    (
+                        pp[facei],
+                        pT[facei],
+                        patchi,
+                        facei
+                    );
+
                 if (this->updateT())
                 {
                     pT[facei] = mixture_.THE(phe[facei], pp[facei], pT[facei]);
                 }
 
                 ppsi[facei] = mixture_.psi(pp[facei], pT[facei]);
-                prho[facei] = mixture_.rho(pp[facei], pT[facei]);
+                prho[facei] = volMixture_.rho(pp[facei], pT[facei]);
                 pmu[facei] = mixture_.mu(pp[facei], pT[facei]);
                 palpha[facei] = mixture_.alphah(pp[facei], pT[facei]);
             }
diff --git a/src/thermophysicalModels/reactionThermo/mixtures/homogeneousMixture/homogeneousMixture.H b/src/thermophysicalModels/reactionThermo/mixtures/homogeneousMixture/homogeneousMixture.H
index 6d77bf2deb..4503b002ef 100644
--- a/src/thermophysicalModels/reactionThermo/mixtures/homogeneousMixture/homogeneousMixture.H
+++ b/src/thermophysicalModels/reactionThermo/mixtures/homogeneousMixture/homogeneousMixture.H
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
+    Copyright (C) 2020      OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -106,6 +107,16 @@ public:
             return mixture(b_[celli]);
         }
 
+        const ThermoType& cellVolMixture
+        (
+            const scalar p,
+            const scalar T,
+            const label celli
+        ) const
+        {
+            return mixture(b_[celli]);
+        }
+
         const ThermoType& patchFaceMixture
         (
             const label patchi,
@@ -115,6 +126,19 @@ public:
             return mixture(b_.boundaryField()[patchi][facei]);
         }
 
+
+        const ThermoType& patchFaceVolMixture
+        (
+            const scalar p,
+            const scalar T,
+            const label patchi,
+            const label facei
+        ) const
+        {
+            return mixture(b_.boundaryField()[patchi][facei]);
+        }
+
+
         const ThermoType& cellReactants(const label) const
         {
             return reactants_;
diff --git a/src/thermophysicalModels/reactionThermo/mixtures/inhomogeneousMixture/inhomogeneousMixture.H b/src/thermophysicalModels/reactionThermo/mixtures/inhomogeneousMixture/inhomogeneousMixture.H
index 2c38501c60..58a130273e 100644
--- a/src/thermophysicalModels/reactionThermo/mixtures/inhomogeneousMixture/inhomogeneousMixture.H
+++ b/src/thermophysicalModels/reactionThermo/mixtures/inhomogeneousMixture/inhomogeneousMixture.H
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
+    Copyright (C) 2020      OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -120,6 +121,16 @@ public:
             return mixture(ft_[celli], b_[celli]);
         }
 
+        const ThermoType& cellVolMixture
+        (
+            const scalar p,
+            const scalar T,
+            const label celli
+        ) const
+        {
+            return mixture(ft_[celli], b_[celli]);
+        }
+
         const ThermoType& patchFaceMixture
         (
             const label patchi,
@@ -133,6 +144,21 @@ public:
             );
         }
 
+        const ThermoType& patchFaceVolMixture
+        (
+            const scalar p,
+            const scalar T,
+            const label patchi,
+            const label facei
+        ) const
+        {
+            return mixture
+            (
+                ft_.boundaryField()[patchi][facei],
+                b_.boundaryField()[patchi][facei]
+            );
+        }
+
         const ThermoType& cellReactants(const label celli) const
         {
             return mixture(ft_[celli], 1);
diff --git a/src/thermophysicalModels/reactionThermo/mixtures/veryInhomogeneousMixture/veryInhomogeneousMixture.H b/src/thermophysicalModels/reactionThermo/mixtures/veryInhomogeneousMixture/veryInhomogeneousMixture.H
index db3354a591..84e16c5b24 100644
--- a/src/thermophysicalModels/reactionThermo/mixtures/veryInhomogeneousMixture/veryInhomogeneousMixture.H
+++ b/src/thermophysicalModels/reactionThermo/mixtures/veryInhomogeneousMixture/veryInhomogeneousMixture.H
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2017 OpenFOAM Foundation
+    Copyright (C) 2020      OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -123,6 +124,16 @@ public:
             return mixture(ft_[celli], fu_[celli]);
         }
 
+        const ThermoType& cellVolMixture
+        (
+            const scalar p,
+            const scalar T,
+            const label celli
+        ) const
+        {
+            return mixture(ft_[celli], fu_[celli]);
+        }
+
         const ThermoType& patchFaceMixture
         (
             const label patchi,
@@ -136,6 +147,22 @@ public:
             );
         }
 
+        const ThermoType& patchFaceVolMixture
+        (
+            const scalar p,
+            const scalar T,
+            const label patchi,
+            const label facei
+        ) const
+        {
+            return mixture
+            (
+                ft_.boundaryField()[patchi][facei],
+                fu_.boundaryField()[patchi][facei]
+            );
+        }
+
+
         const ThermoType& cellReactants(const label celli) const
         {
             return mixture(ft_[celli], ft_[celli]);