Unable to serialize large R*Tree using FlatBuffer

I was trying to Serialize a large R*Tree using the APIs in this Library, but it failed with error :

Exception in thread "main" java.lang.AssertionError: FlatBuffers: cannot grow buffer beyond 2 gigabytes.
at com.google.flatbuffers.FlatBufferBuilder.growByteBuffer(FlatBufferBuilder.java:127)
at com.google.flatbuffers.FlatBufferBuilder.prep(FlatBufferBuilder.java:173)
at com.google.flatbuffers.FlatBufferBuilder.addOffset(FlatBufferBuilder.java:291)
at com.google.flatbuffers.FlatBufferBuilder.addOffset(FlatBufferBuilder.java:562)
at com.github.davidmoten.rtree.fbs.generated.Entry_.addObject(Entry_.java:33)
at com.github.davidmoten.rtree.fbs.generated.Entry_.createEntry_(Entry_.java:26)
at com.github.davidmoten.rtree.fbs.FlatBuffersHelper.addEntries(FlatBuffersHelper.java:77)
at com.github.davidmoten.rtree.fbs.SerializerFlatBuffers.addNode(SerializerFlatBuffers.java:96)
at com.github.davidmoten.rtree.fbs.SerializerFlatBuffers.addNode(SerializerFlatBuffers.java:102)
at com.github.davidmoten.rtree.fbs.SerializerFlatBuffers.addNode(SerializerFlatBuffers.java:102)
at com.github.davidmoten.rtree.fbs.SerializerFlatBuffers.addNode(SerializerFlatBuffers.java:102)
at com.github.davidmoten.rtree.fbs.SerializerFlatBuffers.addNode(SerializerFlatBuffers.java:102)
at com.github.davidmoten.rtree.fbs.SerializerFlatBuffers.addNode(SerializerFlatBuffers.java:102)
at com.github.davidmoten.rtree.fbs.SerializerFlatBuffers.addNode(SerializerFlatBuffers.java:102)
at com.github.davidmoten.rtree.fbs.SerializerFlatBuffers.addNode(SerializerFlatBuffers.java:102)
at com.github.davidmoten.rtree.fbs.SerializerFlatBuffers.addNode(SerializerFlatBuffers.java:102)
at com.github.davidmoten.rtree.fbs.SerializerFlatBuffers.write(SerializerFlatBuffers.java:73)

Seems like FlatBuffers can't serialize large structures with size more than 2GB? Am I mistaken here?
Does this implementation support any other serialization apart from FlatBuffer?
I saw few test cases for Kryo Serialization but don't think if the current structure supports this.
Please guide.