OntModel.add doesn't copy prefixes

[Martin]

Hi,

I do this:
Model tmpModel = ModelFactory.createDefaultModel();
tmpModel.read(ontologyURL);
ontModel.add(tmpModel);

Now ontModel doesn't have the prefixes contained in tmpModel. Am I do 
doing something wrong or do I just have to transfer prefix mapping 
explicitly?

Thx & take care,
martin