diff --git a/src/fvOptions/constraints/fixedTemperatureConstraint/fixedTemperatureConstraint.C b/src/fvOptions/constraints/fixedTemperatureConstraint/fixedTemperatureConstraint.C
index fd3aea1193..f38df30901 100644
--- a/src/fvOptions/constraints/fixedTemperatureConstraint/fixedTemperatureConstraint.C
+++ b/src/fvOptions/constraints/fixedTemperatureConstraint/fixedTemperatureConstraint.C
@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     | Website:  https://openfoam.org
-    \\  /    A nd           | Copyright (C) 2012-2019 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2012-2020 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -70,7 +70,8 @@ Foam::fv::fixedTemperatureConstraint::fixedTemperatureConstraint
     cellSetOption(name, modelType, dict, mesh),
     mode_(temperatureModeNames_.read(coeffs_.lookup("mode"))),
     Tuniform_(nullptr),
-    TName_("T")
+    TName_("T"),
+    phase_(coeffs_.lookupOrDefault<word>("phase", word::null))
 {
     switch (mode_)
     {
@@ -93,12 +94,14 @@ Foam::fv::fixedTemperatureConstraint::fixedTemperatureConstraint
         }
     }
 
-
     // Set the field name to that of the energy field from which the temperature
     // is obtained
 
     const basicThermo& thermo =
-        mesh_.lookupObject<basicThermo>(basicThermo::dictName);
+        mesh_.lookupObject<basicThermo>
+        (
+            IOobject::groupName(basicThermo::dictName, phase_)
+        );
 
     fieldNames_.setSize(1, thermo.he().name());
 
@@ -115,7 +118,10 @@ void Foam::fv::fixedTemperatureConstraint::constrain
 )
 {
     const basicThermo& thermo =
-        mesh_.lookupObject<basicThermo>(basicThermo::dictName);
+        mesh_.lookupObject<basicThermo>
+        (
+            IOobject::groupName(basicThermo::dictName, phase_)
+        );
 
     switch (mode_)
     {
diff --git a/src/fvOptions/constraints/fixedTemperatureConstraint/fixedTemperatureConstraint.H b/src/fvOptions/constraints/fixedTemperatureConstraint/fixedTemperatureConstraint.H
index 5026e6ac53..0b35085774 100644
--- a/src/fvOptions/constraints/fixedTemperatureConstraint/fixedTemperatureConstraint.H
+++ b/src/fvOptions/constraints/fixedTemperatureConstraint/fixedTemperatureConstraint.H
@@ -2,7 +2,7 @@
   =========                 |
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     | Website:  https://openfoam.org
-    \\  /    A nd           | Copyright (C) 2012-2019 OpenFOAM Foundation
+    \\  /    A nd           | Copyright (C) 2012-2020 OpenFOAM Foundation
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
 License
@@ -41,6 +41,8 @@ Usage
 
         // For lookup option
         // T            <Tname>;      // optional temperature field name
+
+        phase           gas; // optional
     }
     \endverbatim
 
@@ -105,6 +107,9 @@ protected:
         //- Temperature field name
         word TName_;
 
+        //- Optional phase name
+        word phase_;
+
 
 public: