diff --git a/src/Pstream/mpi/PstreamGlobals.C b/src/Pstream/mpi/PstreamGlobals.C
index 5fd81abae9ba133a05c104b4856e3f71d98de2c9..0da82d704363812d12a49c840dd31b8b8b69be70 100644
--- a/src/Pstream/mpi/PstreamGlobals.C
+++ b/src/Pstream/mpi/PstreamGlobals.C
@@ -30,11 +30,8 @@ License
 
 // * * * * * * * * * * * * * * Static Data Members * * * * * * * * * * * * * //
 
-Foam::DynamicList<unsigned> Foam::PstreamGlobals::pendingMPIFree_;
-
+Foam::DynamicList<bool> Foam::PstreamGlobals::pendingMPIFree_;
 Foam::DynamicList<MPI_Comm> Foam::PstreamGlobals::MPICommunicators_;
-Foam::DynamicList<MPI_Group> Foam::PstreamGlobals::MPIGroups_;
-
 Foam::DynamicList<MPI_Request> Foam::PstreamGlobals::outstandingRequests_;
 
 
diff --git a/src/Pstream/mpi/PstreamGlobals.H b/src/Pstream/mpi/PstreamGlobals.H
index 276f18932845e2525cddfc7534bfd269b05a21f4..d2ce681ce0b6923aa20b0dfc82b1f4b8eaf327a8 100644
--- a/src/Pstream/mpi/PstreamGlobals.H
+++ b/src/Pstream/mpi/PstreamGlobals.H
@@ -50,26 +50,13 @@ namespace Foam
 namespace PstreamGlobals
 {
 
-//- Internal enumeration to track the state of MPI_Comm, MPI_Group allocation
-//  Handled as bitmasks
-enum allocationTypes : unsigned
-{
-    NonePending = 0u,   // No MPI free is pending
-    CommPending = 1u,   // MPI_Comm_free() is needed
-    GroupPending = 2u   // MPI_Group_free() is needed
-};
-
-// Track if MPI_Comm_free and/or MPI_Group_free are pending for
-// each communicator index (indexes into MPICommunicators_, MPIGroups_)
-extern DynamicList<unsigned> pendingMPIFree_;
+// Track if MPI_Comm_free is needed for communicator index in MPICommunicators_
+extern DynamicList<bool> pendingMPIFree_;
 
 // Current communicators, which may be allocated or predefined
 // (eg, MPI_COMM_SELF, MPI_COMM_WORLD)
 extern DynamicList<MPI_Comm> MPICommunicators_;
 
-// Groups used to create communicators
-extern DynamicList<MPI_Group> MPIGroups_;
-
 //- Outstanding non-blocking operations.
 extern DynamicList<MPI_Request> outstandingRequests_;
 
diff --git a/src/Pstream/mpi/UPstream.C b/src/Pstream/mpi/UPstream.C
index 4555fd62eda59b432fe6c4c74a54c17493b6474d..19587ccd909e9294b1b257a8f3834bbebe198a24 100644
--- a/src/Pstream/mpi/UPstream.C
+++ b/src/Pstream/mpi/UPstream.C
@@ -511,12 +511,8 @@ void Foam::UPstream::allocatePstreamCommunicator
     if (index == PstreamGlobals::MPICommunicators_.size())
     {
         // Extend storage with null values
-
-        PstreamGlobals::
-            pendingMPIFree_.emplace_back(PstreamGlobals::NonePending);
-
+        PstreamGlobals::pendingMPIFree_.emplace_back(false);
         PstreamGlobals::MPICommunicators_.emplace_back(MPI_COMM_NULL);
-        PstreamGlobals::MPIGroups_.emplace_back(MPI_GROUP_NULL);
     }
     else if (index > PstreamGlobals::MPICommunicators_.size())
     {
@@ -538,18 +534,13 @@ void Foam::UPstream::allocatePstreamCommunicator
                 << Foam::exit(FatalError);
         }
 
-        PstreamGlobals::pendingMPIFree_[index] = PstreamGlobals::NonePending;
+        PstreamGlobals::pendingMPIFree_[index] = false;
         PstreamGlobals::MPICommunicators_[index] = MPI_COMM_WORLD;
 
         // TBD: MPI_Comm_dup(MPI_COMM_WORLD, ...);
-        // with pendingMPIFree_[index] = CommPending ...
+        // with pendingMPIFree_[index] = true
         // Note: freePstreamCommunicator may need an update
 
-        MPI_Comm_group
-        (
-            PstreamGlobals::MPICommunicators_[index],
-           &PstreamGlobals::MPIGroups_[index]
-        );
         MPI_Comm_rank
         (
             PstreamGlobals::MPICommunicators_[index],
@@ -572,10 +563,9 @@ void Foam::UPstream::allocatePstreamCommunicator
     {
         // Self communicator (selfComm)
 
-        PstreamGlobals::pendingMPIFree_[index] = PstreamGlobals::NonePending;
+        PstreamGlobals::pendingMPIFree_[index] = false;
         PstreamGlobals::MPICommunicators_[index] = MPI_COMM_SELF;
 
-        MPI_Comm_group(MPI_COMM_SELF, &PstreamGlobals::MPIGroups_[index]);
         MPI_Comm_rank(MPI_COMM_SELF, &myProcNo_[index]);
 
         // Number of ranks is always 1 (self communicator)
@@ -604,16 +594,23 @@ void Foam::UPstream::allocatePstreamCommunicator
     {
         // General sub-communicator
 
-        PstreamGlobals::pendingMPIFree_[index]
-            = (PstreamGlobals::CommPending | PstreamGlobals::GroupPending);
+        PstreamGlobals::pendingMPIFree_[index] = true;
 
-        // Create new group
+        // Starting from parent
+        MPI_Group parent_group;
+        MPI_Comm_group
+        (
+            PstreamGlobals::MPICommunicators_[parentIndex],
+           &parent_group
+        );
+
+        MPI_Group active_group;
         MPI_Group_incl
         (
-            PstreamGlobals::MPIGroups_[parentIndex],
+            parent_group,
             procIDs_[index].size(),
             procIDs_[index].cdata(),
-           &PstreamGlobals::MPIGroups_[index]
+           &active_group
         );
 
         #if defined(MSMPI_VER)
@@ -621,26 +618,29 @@ void Foam::UPstream::allocatePstreamCommunicator
         MPI_Comm_create
         (
             PstreamGlobals::MPICommunicators_[parentIndex],
-            PstreamGlobals::MPIGroups_[index],
-            &PstreamGlobals::MPICommunicators_[index]
+            active_group,
+           &PstreamGlobals::MPICommunicators_[index]
         );
         #else
         // Create new communicator for this group
         MPI_Comm_create_group
         (
             PstreamGlobals::MPICommunicators_[parentIndex],
-            PstreamGlobals::MPIGroups_[index],
+            active_group,
             UPstream::msgType(),
            &PstreamGlobals::MPICommunicators_[index]
         );
         #endif
 
+        // Groups not needed after this...
+        MPI_Group_free(&parent_group);
+        MPI_Group_free(&active_group);
+
         if (PstreamGlobals::MPICommunicators_[index] == MPI_COMM_NULL)
         {
-            // No communicator created, group only
+            // No communicator created
             myProcNo_[index] = -1;
-            PstreamGlobals::
-                pendingMPIFree_[index] = PstreamGlobals::GroupPending;
+            PstreamGlobals::pendingMPIFree_[index] = false;
         }
         else
         {
@@ -681,33 +681,15 @@ void Foam::UPstream::freePstreamCommunicator(const label index)
     {
         if
         (
-            (MPI_COMM_NULL != PstreamGlobals::MPICommunicators_[index])
-         &&
-            (
-                PstreamGlobals::pendingMPIFree_[index]
-              & PstreamGlobals::CommPending
-            )
+            (true == PstreamGlobals::pendingMPIFree_[index])
+         && (MPI_COMM_NULL != PstreamGlobals::MPICommunicators_[index])
         )
         {
             // Free communicator. Sets communicator to MPI_COMM_NULL
             MPI_Comm_free(&PstreamGlobals::MPICommunicators_[index]);
         }
 
-        if
-        (
-            (MPI_GROUP_NULL != PstreamGlobals::MPIGroups_[index])
-         &&
-            (
-                PstreamGlobals::pendingMPIFree_[index]
-              & PstreamGlobals::GroupPending
-            )
-        )
-        {
-            // Free group. Sets group to MPI_GROUP_NULL
-            MPI_Group_free(&PstreamGlobals::MPIGroups_[index]);
-        }
-
-        PstreamGlobals::pendingMPIFree_[index] = PstreamGlobals::NonePending;
+        PstreamGlobals::pendingMPIFree_[index] = false;
     }
 }