diff --git a/src/meshTools/AMIInterpolation/GAMG/interfaceFields/cyclicACMIGAMGInterfaceField/cyclicACMIGAMGInterfaceField.C b/src/meshTools/AMIInterpolation/GAMG/interfaceFields/cyclicACMIGAMGInterfaceField/cyclicACMIGAMGInterfaceField.C
index 02afdbdae6ad35d4392880f4e1741fd858e0d854..5f41ba8cefc3e3ff218b7bff8fde48f01e8a7113 100644
--- a/src/meshTools/AMIInterpolation/GAMG/interfaceFields/cyclicACMIGAMGInterfaceField/cyclicACMIGAMGInterfaceField.C
+++ b/src/meshTools/AMIInterpolation/GAMG/interfaceFields/cyclicACMIGAMGInterfaceField/cyclicACMIGAMGInterfaceField.C
@@ -68,8 +68,8 @@ Foam::cyclicACMIGAMGInterfaceField::cyclicACMIGAMGInterfaceField
     cyclicACMIInterface_(refCast<const cyclicACMIGAMGInterface>(GAMGCp)),
     doTransform_(false),
     rank_(0),
-    sendRequests_(0),
-    recvRequests_(0)
+    sendRequests_(),
+    recvRequests_()
 {
     const cyclicAMILduInterfaceField& p =
         refCast<const cyclicAMILduInterfaceField>(fineInterface);
@@ -90,8 +90,8 @@ Foam::cyclicACMIGAMGInterfaceField::cyclicACMIGAMGInterfaceField
     cyclicACMIInterface_(refCast<const cyclicACMIGAMGInterface>(GAMGCp)),
     doTransform_(doTransform),
     rank_(rank),
-    sendRequests_(0),
-    recvRequests_(0)
+    sendRequests_(),
+    recvRequests_()
 {}
 
 
@@ -105,8 +105,8 @@ Foam::cyclicACMIGAMGInterfaceField::cyclicACMIGAMGInterfaceField
     cyclicACMIInterface_(refCast<const cyclicACMIGAMGInterface>(GAMGCp)),
     doTransform_(readBool(is)),
     rank_(readLabel(is)),
-    sendRequests_(0),
-    recvRequests_(0)
+    sendRequests_(),
+    recvRequests_()
 {}
 
 
@@ -121,8 +121,8 @@ Foam::cyclicACMIGAMGInterfaceField::cyclicACMIGAMGInterfaceField
     cyclicACMIInterface_(refCast<const cyclicACMIGAMGInterface>(GAMGCp)),
     doTransform_(false),
     rank_(0),
-    sendRequests_(0),
-    recvRequests_(0)
+    sendRequests_(),
+    recvRequests_()
 {
     const auto& p = refCast<const cyclicACMILduInterfaceField>(local);
 
@@ -219,8 +219,7 @@ void Foam::cyclicACMIGAMGInterfaceField::initInterfaceMatrixUpdate
 
         // Insert send/receive requests (non-blocking). See e.g.
         // cyclicAMIPolyPatchTemplates.C
-        const label oldWarnComm = UPstream::warnComm;
-        UPstream::warnComm = AMI.comm();
+        const label oldWarnComm = UPstream::commWarn(AMI.comm());
         map.send
         (
             pnf,
@@ -229,7 +228,7 @@ void Foam::cyclicACMIGAMGInterfaceField::initInterfaceMatrixUpdate
             recvRequests_,
             scalarRecvBufs_
         );
-        UPstream::warnComm = oldWarnComm;
+        UPstream::commWarn(oldWarnComm);
     }
 }
 
diff --git a/src/meshTools/AMIInterpolation/GAMG/interfaceFields/cyclicAMIGAMGInterfaceField/cyclicAMIGAMGInterfaceField.C b/src/meshTools/AMIInterpolation/GAMG/interfaceFields/cyclicAMIGAMGInterfaceField/cyclicAMIGAMGInterfaceField.C
index 21a7a0ce655190585bd7511f51c6d41bc944d339..793fe4bfa49ef09f7d3b056ea1d88e7c129b84d4 100644
--- a/src/meshTools/AMIInterpolation/GAMG/interfaceFields/cyclicAMIGAMGInterfaceField/cyclicAMIGAMGInterfaceField.C
+++ b/src/meshTools/AMIInterpolation/GAMG/interfaceFields/cyclicAMIGAMGInterfaceField/cyclicAMIGAMGInterfaceField.C
@@ -68,8 +68,8 @@ Foam::cyclicAMIGAMGInterfaceField::cyclicAMIGAMGInterfaceField
     cyclicAMIInterface_(refCast<const cyclicAMIGAMGInterface>(GAMGCp)),
     doTransform_(false),
     rank_(0),
-    sendRequests_(0),
-    recvRequests_(0)
+    sendRequests_(),
+    recvRequests_()
 {
     const cyclicAMILduInterfaceField& p =
         refCast<const cyclicAMILduInterfaceField>(fineInterface);
@@ -90,8 +90,8 @@ Foam::cyclicAMIGAMGInterfaceField::cyclicAMIGAMGInterfaceField
     cyclicAMIInterface_(refCast<const cyclicAMIGAMGInterface>(GAMGCp)),
     doTransform_(doTransform),
     rank_(rank),
-    sendRequests_(0),
-    recvRequests_(0)
+    sendRequests_(),
+    recvRequests_()
 {}
 
 
@@ -105,8 +105,8 @@ Foam::cyclicAMIGAMGInterfaceField::cyclicAMIGAMGInterfaceField
     cyclicAMIInterface_(refCast<const cyclicAMIGAMGInterface>(GAMGCp)),
     doTransform_(readBool(is)),
     rank_(readLabel(is)),
-    sendRequests_(0),
-    recvRequests_(0)
+    sendRequests_(),
+    recvRequests_()
 {}
 
 
@@ -121,8 +121,8 @@ Foam::cyclicAMIGAMGInterfaceField::cyclicAMIGAMGInterfaceField
     cyclicAMIInterface_(refCast<const cyclicAMIGAMGInterface>(GAMGCp)),
     doTransform_(false),
     rank_(0),
-    sendRequests_(0),   // assume no requests in flight for input field
-    recvRequests_(0)
+    sendRequests_(),    // assume no requests in flight for input field
+    recvRequests_()
 {
     const auto& p = refCast<const cyclicAMILduInterfaceField>(local);
 
@@ -220,8 +220,7 @@ void Foam::cyclicAMIGAMGInterfaceField::initInterfaceMatrixUpdate
 
         // Insert send/receive requests (non-blocking). See e.g.
         // cyclicAMIPolyPatchTemplates.C
-        const label oldWarnComm = UPstream::warnComm;
-        UPstream::warnComm = AMI.comm();
+        const label oldWarnComm = UPstream::commWarn(AMI.comm());
         map.send
         (
             pnf,
@@ -230,7 +229,7 @@ void Foam::cyclicAMIGAMGInterfaceField::initInterfaceMatrixUpdate
             recvRequests_,
             scalarRecvBufs_
         );
-        UPstream::warnComm = oldWarnComm;
+        UPstream::commWarn(oldWarnComm);
     }
 }
 
@@ -314,10 +313,6 @@ void Foam::cyclicAMIGAMGInterfaceField::updateInterfaceMatrix
         // Transform according to the transformation tensors
         transformCoupleField(work, cmpt);
 
-        // Switch on warning if using wrong communicator. Can be removed if
-        // sure all is correct
-        UPstream::warnComm = AMI.comm();
-
         solveScalarField pnf(faceCells.size(), Zero);
         AMI.weightedSum
         (
diff --git a/tutorials/incompressible/pimpleFoam/RAS/oscillatingInletACMI2D/system/fvSolution b/tutorials/incompressible/pimpleFoam/RAS/oscillatingInletACMI2D/system/fvSolution
index 3731355b337571b13d5d036049984f63930a75c6..1d73ceca97e4f16bdcd5e755bcd5e3b707848eb5 100644
--- a/tutorials/incompressible/pimpleFoam/RAS/oscillatingInletACMI2D/system/fvSolution
+++ b/tutorials/incompressible/pimpleFoam/RAS/oscillatingInletACMI2D/system/fvSolution
@@ -22,7 +22,7 @@ solvers
         tolerance       1e-2;
         relTol          0;
         smoother        GaussSeidel;
-        cacheAgglomeration no;
+        //cacheAgglomeration no;    // keep agglom during pimple
         maxIter         50;
     }