diff --git a/source/adios2/core/IO.h b/source/adios2/core/IO.h
index 215dbbfd941c16fbc53c8bbe3df3187b02b8b693..87df704d816b8d62df8180bfb7c72eac1b0399e0 100644
--- a/source/adios2/core/IO.h
+++ b/source/adios2/core/IO.h
@@ -42,7 +42,7 @@ public:
 
     /** from ADIOS class passed to Engine created with Open
      *  if no new communicator is passed */
-    MPI_Comm m_MPIComm = MPI_COMM_SELF;
+    MPI_Comm m_MPIComm;
 
     /** true: extra exceptions checks */
     const bool m_DebugMode = false;
diff --git a/source/adios2/core/VariableBase.cpp b/source/adios2/core/VariableBase.cpp
index 40632a61e7cae1afbaa6781d1e8e036a1a6cb3f1..db50a21db91c2ab96911c5cc74a4b76d7888da84 100644
--- a/source/adios2/core/VariableBase.cpp
+++ b/source/adios2/core/VariableBase.cpp
@@ -112,8 +112,8 @@ void VariableBase::SetMemorySelection(const SelectionBoundingBox &selection)
         }
     }
 
-    ConvertUint64VectorToSizetVector(selection.m_Count, m_MemoryCount);
-    ConvertUint64VectorToSizetVector(selection.m_Start, m_MemoryStart);
+    m_MemoryCount = selection.m_Count;
+    m_MemoryStart = selection.m_Start;
 }
 
 void VariableBase::SetStepSelection(const unsigned int startStep,
diff --git a/source/adios2/toolkit/interop/adios1/ADIOS1Common.h b/source/adios2/toolkit/interop/adios1/ADIOS1Common.h
index 05327d92bfe4281529ec7b5347530f435df62339..c5e2297f4320b67fad2fd4dda198c403635fed15 100644
--- a/source/adios2/toolkit/interop/adios1/ADIOS1Common.h
+++ b/source/adios2/toolkit/interop/adios1/ADIOS1Common.h
@@ -73,7 +73,7 @@ public:
     void Close();
 
 private:
-    MPI_Comm m_MPIComm = MPI_COMM_SELF;
+    MPI_Comm m_MPIComm;
     const bool m_DebugMode = false;
 
     void Init();