diff --git a/Framework/Core/src/RootArrowFilesystem.cxx b/Framework/Core/src/RootArrowFilesystem.cxx
index 7e331814272a6..5f2d21d942d37 100644
--- a/Framework/Core/src/RootArrowFilesystem.cxx
+++ b/Framework/Core/src/RootArrowFilesystem.cxx
@@ -13,6 +13,7 @@
 #include "Framework/RuntimeError.h"
 #include "Framework/Signpost.h"
 #include <Rtypes.h>
+#include <arrow/array/array_nested.h>
 #include <arrow/array/array_primitive.h>
 #include <arrow/array/builder_nested.h>
 #include <arrow/array/builder_primitive.h>
@@ -427,7 +428,7 @@ class TTreeFileWriter : public arrow::dataset::FileWriter
         O2_SIGNPOST_EVENT_EMIT(root_arrow_fs, sid, "finaliseBasketSize", "Branch %s exists and uses %d bytes per entry.",
                                branch->GetName(), valueSize);
         // This should probably lookup the
-        auto column = firstBatch->GetColumnByName(branch->GetName());
+        auto column = firstBatch->GetColumnByName(schema_->field(i)->name());
         auto list = std::static_pointer_cast<arrow::ListArray>(column);
         O2_SIGNPOST_EVENT_EMIT(root_arrow_fs, sid, "finaliseBasketSize", "Branch %s needed. Associated size branch %s and there are %lli entries of size %d in that list.",
                                branch->GetName(), sizeBranch->GetName(), list->length(), valueSize);
@@ -497,8 +498,8 @@ class TTreeFileWriter : public arrow::dataset::FileWriter
         } break;
         case arrow::Type::LIST: {
           valueTypes.push_back(field->type()->field(0)->type());
-          listSizes.back() = 0; // VLA, we need to calculate it on the fly;
           std::string leafList = fmt::format("{}[{}_size]{}", field->name(), field->name(), rootSuffixFromArrow(valueTypes.back()->id()));
+          listSizes.back() = -1; // VLA, we need to calculate it on the fly;
           std::string sizeLeafList = field->name() + "_size/I";
           sizesBranches.push_back(treeStream->CreateBranch((field->name() + "_size").c_str(), sizeLeafList.c_str()));
           branches.push_back(treeStream->CreateBranch(field->name().c_str(), leafList.c_str()));
@@ -765,7 +766,7 @@ arrow::Result<arrow::RecordBatchGenerator> TTreeFileFormat::ScanBatchesAsync(
           typeSize = fixedSizeList->field(0)->type()->byte_width();
         } else if (auto vlaListType = std::dynamic_pointer_cast<arrow::ListType>(physicalField->type())) {
           listSize = -1;
-          typeSize = fixedSizeList->field(0)->type()->byte_width();
+          typeSize = vlaListType->field(0)->type()->byte_width();
         }
         if (listSize == -1) {
           mSizeBranch = branch->GetTree()->GetBranch((std::string{branch->GetName()} + "_size").c_str());
diff --git a/Framework/Core/test/test_Root2ArrowTable.cxx b/Framework/Core/test/test_Root2ArrowTable.cxx
index a659d488ae24a..2b0ab9154250c 100644
--- a/Framework/Core/test/test_Root2ArrowTable.cxx
+++ b/Framework/Core/test/test_Root2ArrowTable.cxx
@@ -322,12 +322,26 @@ bool validateContents(std::shared_ptr<arrow::RecordBatch> batch)
       REQUIRE(bool_array->Value(1) == (i % 5 == 0));
     }
   }
+
+  {
+    auto list_array = std::static_pointer_cast<arrow::ListArray>(batch->GetColumnByName("vla"));
+
+    REQUIRE(list_array->length() == 100);
+    for (int64_t i = 0; i < list_array->length(); i++) {
+      auto value_slice = list_array->value_slice(i);
+      REQUIRE(value_slice->length() == (i % 10));
+      auto int_array = std::static_pointer_cast<arrow::Int32Array>(value_slice);
+      for (size_t j = 0; j < value_slice->length(); j++) {
+        REQUIRE(int_array->Value(j) == j);
+      }
+    }
+  }
   return true;
 }
 
 bool validateSchema(std::shared_ptr<arrow::Schema> schema)
 {
-  REQUIRE(schema->num_fields() == 9);
+  REQUIRE(schema->num_fields() == 10);
   REQUIRE(schema->field(0)->type()->id() == arrow::float32()->id());
   REQUIRE(schema->field(1)->type()->id() == arrow::float32()->id());
   REQUIRE(schema->field(2)->type()->id() == arrow::float32()->id());
@@ -337,6 +351,7 @@ bool validateSchema(std::shared_ptr<arrow::Schema> schema)
   REQUIRE(schema->field(6)->type()->id() == arrow::fixed_size_list(arrow::int32(), 2)->id());
   REQUIRE(schema->field(7)->type()->id() == arrow::boolean()->id());
   REQUIRE(schema->field(8)->type()->id() == arrow::fixed_size_list(arrow::boolean(), 2)->id());
+  REQUIRE(schema->field(9)->type()->id() == arrow::list(arrow::int32())->id());
   return true;
 }
 
@@ -390,6 +405,8 @@ TEST_CASE("RootTree2Dataset")
     Int_t ev;
     bool oneBool;
     bool manyBool[2];
+    int vla[10] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9};
+    int vlaSize = 0;
 
     t->Branch("px", &px, "px/F");
     t->Branch("py", &py, "py/F");
@@ -400,6 +417,8 @@ TEST_CASE("RootTree2Dataset")
     t->Branch("ij", ij, "ij[2]/I");
     t->Branch("bools", &oneBool, "bools/O");
     t->Branch("manyBools", &manyBool, "manyBools[2]/O");
+    t->Branch("vla_size", &vlaSize, "vla_size/I");
+    t->Branch("vla", vla, "vla[vla_size]/I");
     // fill the tree
     for (Int_t i = 0; i < 100; i++) {
       xyz[0] = 1;
@@ -415,9 +434,11 @@ TEST_CASE("RootTree2Dataset")
       oneBool = (i % 3 == 0);
       manyBool[0] = (i % 4 == 0);
       manyBool[1] = (i % 5 == 0);
+      vlaSize = i % 10;
       t->Fill();
     }
   }
+  f->Write();
 
   size_t totalSizeCompressed = 0;
   size_t totalSizeUncompressed = 0;
@@ -428,16 +449,7 @@ TEST_CASE("RootTree2Dataset")
   auto schemaOpt = format->Inspect(source);
   REQUIRE(schemaOpt.ok());
   auto schema = *schemaOpt;
-  REQUIRE(schema->num_fields() == 9);
-  REQUIRE(schema->field(0)->type()->id() == arrow::float32()->id());
-  REQUIRE(schema->field(1)->type()->id() == arrow::float32()->id());
-  REQUIRE(schema->field(2)->type()->id() == arrow::float32()->id());
-  REQUIRE(schema->field(3)->type()->id() == arrow::float64()->id());
-  REQUIRE(schema->field(4)->type()->id() == arrow::int32()->id());
-  REQUIRE(schema->field(5)->type()->id() == arrow::fixed_size_list(arrow::float32(), 3)->id());
-  REQUIRE(schema->field(6)->type()->id() == arrow::fixed_size_list(arrow::int32(), 2)->id());
-  REQUIRE(schema->field(7)->type()->id() == arrow::boolean()->id());
-  REQUIRE(schema->field(8)->type()->id() == arrow::fixed_size_list(arrow::boolean(), 2)->id());
+  validateSchema(schema);
 
   auto fragment = format->MakeFragment(source, {}, schema);
   REQUIRE(fragment.ok());
@@ -448,41 +460,9 @@ TEST_CASE("RootTree2Dataset")
   auto batches = (*scanner)();
   auto result = batches.result();
   REQUIRE(result.ok());
-  REQUIRE((*result)->columns().size() == 9);
+  REQUIRE((*result)->columns().size() == 10);
   REQUIRE((*result)->num_rows() == 100);
-
-  {
-    auto int_array = std::static_pointer_cast<arrow::Int32Array>((*result)->GetColumnByName("ev"));
-    for (int64_t j = 0; j < int_array->length(); j++) {
-      REQUIRE(int_array->Value(j) == j + 1);
-    }
-  }
-
-  {
-    auto list_array = std::static_pointer_cast<arrow::FixedSizeListArray>((*result)->GetColumnByName("xyz"));
-
-    // Iterate over the FixedSizeListArray
-    for (int64_t i = 0; i < list_array->length(); i++) {
-      auto value_slice = list_array->value_slice(i);
-      auto float_array = std::static_pointer_cast<arrow::FloatArray>(value_slice);
-
-      REQUIRE(float_array->Value(0) == 1);
-      REQUIRE(float_array->Value(1) == 2);
-      REQUIRE(float_array->Value(2) == i + 1);
-    }
-  }
-
-  {
-    auto list_array = std::static_pointer_cast<arrow::FixedSizeListArray>((*result)->GetColumnByName("ij"));
-
-    // Iterate over the FixedSizeListArray
-    for (int64_t i = 0; i < list_array->length(); i++) {
-      auto value_slice = list_array->value_slice(i);
-      auto int_array = std::static_pointer_cast<arrow::Int32Array>(value_slice);
-      REQUIRE(int_array->Value(0) == i);
-      REQUIRE(int_array->Value(1) == i + 1);
-    }
-  }
+  validateContents(*result);
 
   auto* output = new TMemFile("foo", "RECREATE");
   auto outFs = std::make_shared<TFileFileSystem>(output, 0);
@@ -497,31 +477,31 @@ TEST_CASE("RootTree2Dataset")
   auto success = writer->get()->Write(*result);
   auto rootDestination = std::dynamic_pointer_cast<TDirectoryFileOutputStream>(*destination);
 
-  REQUIRE(success.ok());
-  // Let's read it back...
-  arrow::dataset::FileSource source2("/DF_3", outFs);
-  auto newTreeFS = outFs->GetSubFilesystem(source2);
-
-  REQUIRE(format->IsSupported(source) == true);
-
-  auto schemaOptWritten = format->Inspect(source);
-  REQUIRE(schemaOptWritten.ok());
-  auto schemaWritten = *schemaOptWritten;
-  REQUIRE(validateSchema(schemaWritten));
-
-  auto fragmentWritten = format->MakeFragment(source, {}, schema);
-  REQUIRE(fragmentWritten.ok());
-  auto optionsWritten = std::make_shared<arrow::dataset::ScanOptions>();
-  options->dataset_schema = schemaWritten;
-  auto scannerWritten = format->ScanBatchesAsync(optionsWritten, *fragment);
-  REQUIRE(scannerWritten.ok());
-  auto batchesWritten = (*scanner)();
-  auto resultWritten = batches.result();
-  REQUIRE(resultWritten.ok());
-  REQUIRE((*resultWritten)->columns().size() == 9);
-  REQUIRE((*resultWritten)->num_rows() == 100);
-  validateContents(*resultWritten);
-
+  SECTION("Read tree")
   {
+    REQUIRE(success.ok());
+    // Let's read it back...
+    arrow::dataset::FileSource source2("/DF_3", outFs);
+    auto newTreeFS = outFs->GetSubFilesystem(source2);
+
+    REQUIRE(format->IsSupported(source) == true);
+
+    auto schemaOptWritten = format->Inspect(source);
+    REQUIRE(schemaOptWritten.ok());
+    auto schemaWritten = *schemaOptWritten;
+    REQUIRE(validateSchema(schemaWritten));
+
+    auto fragmentWritten = format->MakeFragment(source, {}, schema);
+    REQUIRE(fragmentWritten.ok());
+    auto optionsWritten = std::make_shared<arrow::dataset::ScanOptions>();
+    options->dataset_schema = schemaWritten;
+    auto scannerWritten = format->ScanBatchesAsync(optionsWritten, *fragment);
+    REQUIRE(scannerWritten.ok());
+    auto batchesWritten = (*scanner)();
+    auto resultWritten = batches.result();
+    REQUIRE(resultWritten.ok());
+    REQUIRE((*resultWritten)->columns().size() == 10);
+    REQUIRE((*resultWritten)->num_rows() == 100);
+    validateContents(*resultWritten);
   }
 }