diff --git a/src/thermophysicalModels/specie/specie/specieI.H b/src/thermophysicalModels/specie/specie/specieI.H
index 780e7328ba..222ed14d8a 100644
--- a/src/thermophysicalModels/specie/specie/specieI.H
+++ b/src/thermophysicalModels/specie/specie/specieI.H
@@ -161,15 +161,18 @@ inline specie operator==(const specie& st1, const specie& st2)
 
     const scalar diffRW = st2.Y_/st2.molWeight_ - st1.Y_/st1.molWeight_;
 
-    // if (mag(diffRW) > SMALL)
-    // {
-    //     molWeight = diffY/diffRW;
-    // }
-
+    #ifdef __clang__
     // Using intermediate volatile bool to prevent compiler optimising out the
     // if block (above) - CLANG 3.7.1
     volatile const bool valid = (mag(diffRW) > SMALL);
     const scalar molWeight = valid ? diffY/diffRW : GREAT;
+    #else
+    scalar molWeight = GREAT;
+    if (mag(diffRW) > SMALL)
+    {
+         molWeight = diffY/diffRW;
+    }
+    #endif
 
     return specie(diffY, molWeight);
 }
diff --git a/src/thermophysicalModels/specie/thermo/sensibleInternalEnergy/sensibleInternalEnergy.H b/src/thermophysicalModels/specie/thermo/sensibleInternalEnergy/sensibleInternalEnergy.H
index 9b2f97b053..04d42aa018 100644
--- a/src/thermophysicalModels/specie/thermo/sensibleInternalEnergy/sensibleInternalEnergy.H
+++ b/src/thermophysicalModels/specie/thermo/sensibleInternalEnergy/sensibleInternalEnergy.H
@@ -3,7 +3,7 @@
   \\      /  F ield         | OpenFOAM: The Open Source CFD Toolbox
    \\    /   O peration     |
     \\  /    A nd           | Copyright (C) 2012-2017 OpenFOAM Foundation
-     \\/     M anipulation  |
+     \\/     M anipulation  | Copyright (C) 2018 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -42,7 +42,7 @@ namespace Foam
 {
 
 /*---------------------------------------------------------------------------*\
-                       Class sensibleInternalEnergy Declaration
+                   Class sensibleInternalEnergy Declaration
 \*---------------------------------------------------------------------------*/
 
 template<class Thermo>
@@ -51,11 +51,9 @@ class sensibleInternalEnergy
 
 public:
 
-    // Constructors
-
-        //- Construct
-        sensibleInternalEnergy()
-        {}
+    //- Constructor
+    sensibleInternalEnergy()
+    {}
 
 
     // Member Functions
@@ -66,6 +64,7 @@ public:
             return "sensibleInternalEnergy";
         }
 
+
         // Fundamental properties
 
             static word name()
@@ -81,10 +80,17 @@ public:
                 const scalar T
             ) const
             {
+                #ifdef __clang__
+                // Using volatile to prevent compiler optimisations leading to
+                // a sigfpe
+                volatile const scalar cv = thermo.Cv(p, T);
+                return cv;
+                #else
                 return thermo.Cv(p, T);
+                #endif
             }
 
-            //- Cp/Cv []
+            //- Ratio of specific heats Cp/Cv []
             scalar CpByCpv
             (
                 const Thermo& thermo,
@@ -92,7 +98,14 @@ public:
                 const scalar T
             ) const
             {
+                #ifdef __clang__
+                // Using volatile to prevent compiler optimisations leading to
+                // a sigfpe
+                volatile const scalar gamma = thermo.gamma(p, T);
+                return gamma;
+                #else
                 return thermo.gamma(p, T);
+                #endif
             }
 
             //- Sensible internal energy [J/kg]
@@ -103,11 +116,18 @@ public:
                 const scalar T
             ) const
             {
+                #ifdef __clang__
+                // Using volatile to prevent compiler optimisations leading to
+                // a sigfpe
+                volatile const scalar es = thermo.Es(p, T);
+                return es;
+                #else
                 return thermo.Es(p, T);
+                #endif
             }
 
-            //- Temperature from sensible internal energy
-            //  given an initial temperature T0
+            //- Temperature from sensible internal energy given an initial
+            //- temperature T0 [K]
             scalar THE
             (
                 const Thermo& thermo,
@@ -116,7 +136,14 @@ public:
                 const scalar T0
             ) const
             {
+                #ifdef __clang__
+                // Using volatile to prevent compiler optimisations leading to
+                // a sigfpe
+                volatile const scalar tes = thermo.TEs(e, p, T0);
+                return tes;
+                #else
                 return thermo.TEs(e, p, T0);
+                #endif
             }
 };