diff --git a/src/overset/oversetMesh/oversetAdjustPhi/oversetAdjustPhi.C b/src/overset/oversetMesh/oversetAdjustPhi/oversetAdjustPhi.C
index 31086ad42..2f40298be 100644
--- a/src/overset/oversetMesh/oversetAdjustPhi/oversetAdjustPhi.C
+++ b/src/overset/oversetMesh/oversetAdjustPhi/oversetAdjustPhi.C
@@ -59,7 +59,7 @@ void Foam::oversetAdjustPhi
     const unallocLabelList& neighbour = mesh.neighbour();
 
     // Get region split to identify separate mesh components
-    const labelList& regionID = om.regionID();
+    const scalarField& regionID = om.regionID().internalField();
 
     // Sum up incoming and outgoing flux
     scalar fringeIn = 0;
@@ -80,8 +80,12 @@ void Foam::oversetAdjustPhi
         {
             // Internal face
 
-            // Debug check
-            if (regionID[owner[curFace]] != regionID[neighbour[curFace]])
+            // Debug check. Note: use notEqual since we are comparing two
+            // scalars
+            if
+            (
+                notEqual(regionID[owner[curFace]], regionID[neighbour[curFace]])
+            )
             {
                 FatalErrorIn
                 (
diff --git a/src/overset/oversetMesh/oversetAdjustPhi/regionWiseOversetAdjustPhi.C b/src/overset/oversetMesh/oversetAdjustPhi/regionWiseOversetAdjustPhi.C
index 21d25cb47..73e682e49 100644
--- a/src/overset/oversetMesh/oversetAdjustPhi/regionWiseOversetAdjustPhi.C
+++ b/src/overset/oversetMesh/oversetAdjustPhi/regionWiseOversetAdjustPhi.C
@@ -60,7 +60,7 @@ void Foam::regionWiseOversetAdjustPhi
     const unallocLabelList& neighbour = mesh.neighbour();
 
     // Get region split to identify separate mesh components
-    const labelList& regionID = om.regionID();
+    const scalarField& regionID = om.regionID().internalField();
 
     // Incoming and outgoing region fluxes
     scalarField regionIn(om.regions().size(), 0);
@@ -94,7 +94,7 @@ void Foam::regionWiseOversetAdjustPhi
             // scaled
             forAll (phip, i)
             {
-                // Get current region index
+                // Get current region index. Note: conversion to label
                 const label curRegion = regionID[fc[i]];
 
                 if (phip[i] < 0.0)
@@ -124,11 +124,12 @@ void Foam::regionWiseOversetAdjustPhi
         {
             // Internal face
 
-            // Get region index
+            // Get region index. Note: conversion to label
             const label curRegion = regionID[owner[curFace]];
 
-            // Check whether owner and neighbour belong to the same region
-            if (curRegion != regionID[neighbour[curFace]])
+            // Check whether owner and neighbour belong to the same region.
+            // Note: use notEqual function since we are comparing two scalars
+            if (notEqual(curRegion, regionID[neighbour[curFace]]))
             {
                 FatalErrorIn
                 (
@@ -210,7 +211,7 @@ void Foam::regionWiseOversetAdjustPhi
                 {
                     // Processor patch, master side
 
-                    // Get region index
+                    // Get region index. Note: conversion to label
                     const label curRegion =
                         regionID[mesh.boundary()[patchI].faceCells()[faceI]];
 
@@ -321,7 +322,7 @@ void Foam::regionWiseOversetAdjustPhi
         {
             // Internal face
 
-            // Get region index
+            // Get region index. Note: conversion to label
             const label curRegion = regionID[owner[curFace]];
 
             // Get reference to the flux for scaling
@@ -358,7 +359,7 @@ void Foam::regionWiseOversetAdjustPhi
 
             if (procPatch.master()) // Owner side
             {
-                // Get region index
+                // Get region index. Note: conversion to label
                 const label curRegion =
                     regionID[mesh.boundary()[patchI].faceCells()[faceI]];
 
@@ -374,7 +375,7 @@ void Foam::regionWiseOversetAdjustPhi
             }
             else // Neighbouring processor side
             {
-                // Get region index
+                // Get region index. Note: conversion to label
                 const label curRegion =
                     regionID[mesh.boundary()[patchI].faceCells()[faceI]];
 
diff --git a/src/overset/oversetMesh/oversetMesh/oversetMesh.H b/src/overset/oversetMesh/oversetMesh/oversetMesh.H
index 19bb07a72..1cc7092d0 100644
--- a/src/overset/oversetMesh/oversetMesh/oversetMesh.H
+++ b/src/overset/oversetMesh/oversetMesh/oversetMesh.H
@@ -121,8 +121,9 @@ private:
             //- Return overset type indicator field
             mutable volScalarField* oversetTypesPtr_;
 
-            //- Region ID: region index for each cell
-            mutable labelList* regionIDPtr_;
+            //- Region ID: region index for each cell as a volScalarField for
+            //  visualization. VV, 15/Apr/2019
+            mutable volScalarField* regionIDPtr_;
 
 
         // Overset discretisation support
@@ -286,7 +287,7 @@ public:
             const volScalarField& oversetTypes() const;
 
             //- Return region indicator
-            const labelList& regionID() const;
+            const volScalarField& regionID() const;
 
 
         // Overset discretisation support
diff --git a/src/overset/oversetMesh/oversetMesh/oversetMeshAddressing.C b/src/overset/oversetMesh/oversetMesh/oversetMeshAddressing.C
index a3bd410cd..f59e5e030 100644
--- a/src/overset/oversetMesh/oversetMesh/oversetMeshAddressing.C
+++ b/src/overset/oversetMesh/oversetMesh/oversetMeshAddressing.C
@@ -27,6 +27,7 @@ License
 #include "surfaceFields.H"
 #include "volFields.H"
 #include "polyPatchID.H"
+#include "oversetFvPatchFields.H"
 #include "demandDrivenData.H"
 
 // * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
@@ -190,24 +191,52 @@ void Foam::oversetMesh::calcDomainMarkup() const
         }
     }
 
-    // Region ID
-    regionIDPtr_ = new labelList(mesh().nCells(), -1);
-    labelList& rID = *regionIDPtr_;
-
-    // Mark regions
+    // Region ID, initialized with -1 for sanity check later on
+    regionIDPtr_ = new volScalarField
+    (
+        IOobject
+        (
+            "regionIndex",
+            mesh().time().timeName(),
+            mesh(),
+            IOobject::NO_READ,
+            IOobject::AUTO_WRITE
+        ),
+        mesh(),
+        dimensionedScalar("minusOne", dimless, -1.0),
+        "zeroGradient"
+    );
+    volScalarField& regionID = *regionIDPtr_;
+    scalarField& regionIDIn = regionID.internalField();
 
+    // Mark regions (internal field)
     forAll (regions_, regionI)
     {
         const labelList& curCells = regions_[regionI].zone();
 
         forAll (curCells, curCellI)
         {
-            rID[curCells[curCellI]] = regionI;
+            regionIDIn[curCells[curCellI]] = regionI;
+        }
+    }
+
+    // Update boundary values, making sure that we skip the overset patch
+    volScalarField::GeometricBoundaryField& regionIDb =
+        regionID.boundaryField();
+
+    forAll (regionIDb, patchI)
+    {
+        // Get the patch field
+        fvPatchScalarField& ripf = regionIDb[patchI];
+
+        if (!isA<oversetFvPatchScalarField>(ripf))
+        {
+            ripf = ripf.patchInternalField();
         }
     }
 
     // Check regions
-    if (min(rID) < 0)
+    if (min(regionID).value() < 0)
     {
         FatalErrorIn("void oversetMesh::calcDomainMarkup() const")
             << "Found cells without region ID.  Please check overset setup"
@@ -1166,7 +1195,7 @@ const Foam::volScalarField& Foam::oversetMesh::oversetTypes() const
 }
 
 
-const Foam::labelList& Foam::oversetMesh::regionID() const
+const Foam::volScalarField& Foam::oversetMesh::regionID() const
 {
     if (!regionIDPtr_)
     {