Failure adding graph to remote SPARQL store

Question

I am trying to add triples to a remote SPARQL repository, using Python and rdflib 4.2.2.

Adding statement-wise works:

gsu = rdflib.plugins.stores.sparqlstore.SPARQLUpdateStore(sparql_endpoint, update_endpoint, bNodeAsURI=False, sparql11=True, context_aware=False)
for stmt in subGraph: 
    gsu.add( stmt )

But I think it would be more efficient to add graph-wise, i.e

remoteGraph = rdflib.Graph(gsu)
remoteGraph.add( subGraph )

Unfortunatley this resutls in the error: ValueError: too many values to unpack

Did someone have success in adding a graph to a remote repo?