diff --git a/source/adios2/mpidummy.cpp b/source/adios2/mpidummy.cpp
index 75f76646a12d8c80e149ca11e2cf5be46d94c7d2..c6730df1c9a7d60c8d48b9cf8f4a74faa99b8ca5 100644
--- a/source/adios2/mpidummy.cpp
+++ b/source/adios2/mpidummy.cpp
@@ -329,9 +329,10 @@ int MPI_File_read(MPI_File fh, void *buf, int count, MPI_Datatype datatype,
     if (bytes_read != bytes_to_read)
     {
         std::snprintf(mpierrmsg, MPI_MAX_ERROR_STRING,
-                      "could not read %" PRId64 " bytes. read only: %" PRId64
+                      "could not read %llu bytes. read only: %llu"
                       "\n",
-                      bytes_to_read, bytes_read);
+                      (unsigned long long)bytes_to_read,
+                      (unsigned long long)bytes_read);
         return -2;
     }
     *status = bytes_read;
diff --git a/testing/adios2/engine/SmallTestData.h b/testing/adios2/engine/SmallTestData.h
index d7f736582dabc3eedc9c377973461e5578cc1260..05de0729e8e7fdf1ba957942892a24a945722082 100644
--- a/testing/adios2/engine/SmallTestData.h
+++ b/testing/adios2/engine/SmallTestData.h
@@ -10,21 +10,21 @@
 struct SmallTestData
 {
     std::array<char, 10> I8 = {{0, 1, -2, 3, -4, 5, -6, 7, -8, 9}};
-    std::array<int16_t, 10> I16 = {
+    std::array<short, 10> I16 = {
         {512, 513, -510, 515, -508, 517, -506, 519, -504, 521}};
-    std::array<int32_t, 10> I32 = {{131072, 131073, -131070, 131075, -131068,
-                                    131077, -131066, 131079, -131064, 131081}};
-    std::array<int64_t, 10> I64 = {
+    std::array<int, 10> I32 = {{131072, 131073, -131070, 131075, -131068,
+                                131077, -131066, 131079, -131064, 131081}};
+    std::array<long int, 10> I64 = {
         {8589934592, 8589934593, -8589934590, 8589934595, -8589934588,
          8589934597, -8589934586, 8589934599, -8589934584, 8589934601}};
     std::array<unsigned char, 10> U8 = {
         {128, 129, 130, 131, 132, 133, 134, 135, 136, 137}};
-    std::array<uint16_t, 10> U16 = {
+    std::array<unsigned short, 10> U16 = {
         {32768, 32769, 32770, 32771, 32772, 32773, 32774, 32775, 32776, 32777}};
-    std::array<uint32_t, 10> U32 = {
+    std::array<unsigned int, 10> U32 = {
         {2147483648, 2147483649, 2147483650, 2147483651, 2147483652, 2147483653,
          2147483654, 2147483655, 2147483656, 2147483657}};
-    std::array<uint64_t, 10> U64 = {
+    std::array<unsigned long int, 10> U64 = {
         {9223372036854775808UL, 9223372036854775809UL, 9223372036854775810UL,
          9223372036854775811UL, 9223372036854775812UL, 9223372036854775813UL,
          9223372036854775814UL, 9223372036854775815UL, 9223372036854775816UL,