diff --git a/src/OpenFOAM/expressions/exprResult/exprResult.C b/src/OpenFOAM/expressions/exprResult/exprResult.C
index afe1ae9b4c..0665403522 100644
--- a/src/OpenFOAM/expressions/exprResult/exprResult.C
+++ b/src/OpenFOAM/expressions/exprResult/exprResult.C
@@ -6,7 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2012-2018 Bernhard Gschaider <bgschaid@hfd-research.com>
-    Copyright (C) 2019-2020 OpenCFD Ltd.
+    Copyright (C) 2019-2021 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -31,6 +31,7 @@ License
 #include "tensor.H"
 #include "symmTensor.H"
 #include "sphericalTensor.H"
+#include "Switch.H"
 #include "addToRunTimeSelectionTable.H"
 
 // * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
diff --git a/src/OpenFOAM/primitives/functions/Math/erfInv.C b/src/OpenFOAM/primitives/functions/Math/erfInv.C
index ccce80dbec..1c5b01497c 100644
--- a/src/OpenFOAM/primitives/functions/Math/erfInv.C
+++ b/src/OpenFOAM/primitives/functions/Math/erfInv.C
@@ -27,6 +27,7 @@ License
 
 #include "MathFunctions.H"
 #include "mathematicalConstants.H"
+#include "error.H"
 
 // * * * * * * * * * * * * * * * Global Functions * * * * * * * * * * * * * * //
 
diff --git a/src/OpenFOAM/primitives/functions/Math/incGamma.C b/src/OpenFOAM/primitives/functions/Math/incGamma.C
index fcee586dda..0146bb14a1 100644
--- a/src/OpenFOAM/primitives/functions/Math/incGamma.C
+++ b/src/OpenFOAM/primitives/functions/Math/incGamma.C
@@ -34,6 +34,7 @@ Description
 
 #include "MathFunctions.H"
 #include "mathematicalConstants.H"
+#include "error.H"
 #include <cmath>
 
 // * * * * * * * * * * * * * * * Local Functions * * * * * * * * * * * * * * //
diff --git a/src/OpenFOAM/primitives/functions/Math/invIncGamma.C b/src/OpenFOAM/primitives/functions/Math/invIncGamma.C
index 3a38e3d7c3..58897f62d2 100644
--- a/src/OpenFOAM/primitives/functions/Math/invIncGamma.C
+++ b/src/OpenFOAM/primitives/functions/Math/invIncGamma.C
@@ -34,6 +34,7 @@ Description
 
 #include "MathFunctions.H"
 #include "mathematicalConstants.H"
+#include "error.H"
 
 using namespace Foam::constant::mathematical;