diff --git a/src/OpenFOAM/global/constants/atomic/atomicConstants.C b/src/OpenFOAM/global/constants/atomic/atomicConstants.C
index 3e021aff2b..83a1291c85 100644
--- a/src/OpenFOAM/global/constants/atomic/atomicConstants.C
+++ b/src/OpenFOAM/global/constants/atomic/atomicConstants.C
@@ -38,9 +38,6 @@ namespace Foam
 namespace constant
 {
 
-const char* const atomic::group = "atomic";
-
-
 // Note: cannot use dimless etc. since not guaranteed to be constructed
 defineDimensionedConstantWithDefault
 (
diff --git a/src/OpenFOAM/global/constants/atomic/atomicConstants.H b/src/OpenFOAM/global/constants/atomic/atomicConstants.H
index 98b24ba1f2..2329149218 100644
--- a/src/OpenFOAM/global/constants/atomic/atomicConstants.H
+++ b/src/OpenFOAM/global/constants/atomic/atomicConstants.H
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011 OpenFOAM Foundation
+    Copyright (C) 2020 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -48,7 +49,7 @@ namespace atomic
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
     //- Group name for atomic constants
-    extern const char* const group;
+    constexpr const char* const group = "atomic";
 
     //- Fine-structure constant: default SI units: []
     extern const dimensionedScalar alpha;
diff --git a/src/OpenFOAM/global/constants/electromagnetic/electromagneticConstants.C b/src/OpenFOAM/global/constants/electromagnetic/electromagneticConstants.C
index 8395701a1c..2ff36af147 100644
--- a/src/OpenFOAM/global/constants/electromagnetic/electromagneticConstants.C
+++ b/src/OpenFOAM/global/constants/electromagnetic/electromagneticConstants.C
@@ -38,9 +38,6 @@ namespace Foam
 namespace constant
 {
 
-const char* const electromagnetic::group = "electromagnetic";
-
-
 defineDimensionedConstantWithDefault
 (
     electromagnetic::group,
diff --git a/src/OpenFOAM/global/constants/electromagnetic/electromagneticConstants.H b/src/OpenFOAM/global/constants/electromagnetic/electromagneticConstants.H
index f1867aadf1..9922d2d064 100644
--- a/src/OpenFOAM/global/constants/electromagnetic/electromagneticConstants.H
+++ b/src/OpenFOAM/global/constants/electromagnetic/electromagneticConstants.H
@@ -48,7 +48,7 @@ namespace electromagnetic
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
     //- Group name for electromagnetic constants
-    extern const char* const group;
+    constexpr const char* const group = "electromagnetic";
 
     //- Magnetic constant/permeability of free space: default SI units: [H/m]
     extern const dimensionedScalar mu0;
diff --git a/src/OpenFOAM/global/constants/mathematical/mathematicalConstants.H b/src/OpenFOAM/global/constants/mathematical/mathematicalConstants.H
index fd6af5051a..c850efa976 100644
--- a/src/OpenFOAM/global/constants/mathematical/mathematicalConstants.H
+++ b/src/OpenFOAM/global/constants/mathematical/mathematicalConstants.H
@@ -48,6 +48,7 @@ namespace mathematical
 
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
+    //- Group name for mathematical constants
     constexpr const char* const group = "mathematical";
 
     constexpr scalar e(M_E);
diff --git a/src/OpenFOAM/global/constants/physicoChemical/physicoChemicalConstants.C b/src/OpenFOAM/global/constants/physicoChemical/physicoChemicalConstants.C
index 2089d1e1ec..6259c8392d 100644
--- a/src/OpenFOAM/global/constants/physicoChemical/physicoChemicalConstants.C
+++ b/src/OpenFOAM/global/constants/physicoChemical/physicoChemicalConstants.C
@@ -39,8 +39,6 @@ namespace Foam
 namespace constant
 {
 
-const char* const physicoChemical::group = "physicoChemical";
-
 defineDimensionedConstantWithDefault
 (
     physicoChemical::group,
diff --git a/src/OpenFOAM/global/constants/physicoChemical/physicoChemicalConstants.H b/src/OpenFOAM/global/constants/physicoChemical/physicoChemicalConstants.H
index 6ccfca8329..fc1c0b7bb7 100644
--- a/src/OpenFOAM/global/constants/physicoChemical/physicoChemicalConstants.H
+++ b/src/OpenFOAM/global/constants/physicoChemical/physicoChemicalConstants.H
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011-2015 OpenFOAM Foundation
+    Copyright (C) 2020 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -48,7 +49,7 @@ namespace physicoChemical
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
     //- Group name for physico-chemical constants
-    extern const char* const group;
+    constexpr const char* const group = "physicoChemical";
 
     //- Universal gas constant: default SI units: [J/mol/K]
     extern const dimensionedScalar R;
diff --git a/src/OpenFOAM/global/constants/universal/universalConstants.C b/src/OpenFOAM/global/constants/universal/universalConstants.C
index 4f8335f31c..6007602447 100644
--- a/src/OpenFOAM/global/constants/universal/universalConstants.C
+++ b/src/OpenFOAM/global/constants/universal/universalConstants.C
@@ -36,9 +36,6 @@ namespace Foam
 namespace constant
 {
 
-const char* const universal::group = "universal";
-
-
 // Note: cannot use dimless etc. since not guaranteed to be constructed
 defineDimensionedConstantWithDefault
 (
diff --git a/src/OpenFOAM/global/constants/universal/universalConstants.H b/src/OpenFOAM/global/constants/universal/universalConstants.H
index b3d9263f0d..2f9c2961b1 100644
--- a/src/OpenFOAM/global/constants/universal/universalConstants.H
+++ b/src/OpenFOAM/global/constants/universal/universalConstants.H
@@ -6,6 +6,7 @@
      \\/     M anipulation  |
 -------------------------------------------------------------------------------
     Copyright (C) 2011 OpenFOAM Foundation
+    Copyright (C) 2020 OpenCFD Ltd.
 -------------------------------------------------------------------------------
 License
     This file is part of OpenFOAM.
@@ -48,7 +49,7 @@ namespace universal
 // * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * * //
 
     //- Group name for universal constants
-    extern const char* const group;
+    constexpr const char* const group = "universal";
 
     //- Reduced Planck constant: default SI units: [J/s]
     extern const dimensionedScalar hr;