Bug: Prefix not used when local starts with a digit

[dukesook]

I'm calling:

librdf_serializer_set_namespace(serializer, "imh", "http://ontology.mil/foundry/IMH_");

for the desired output:

@prefix imh: <http://ontology.mil/foundry/IMH_> .

<urn:uuid0442f858-1c1b-4031-8e03-8ed8aba08b22>
    imh:0001430 4221751.220000 ;
    imh:0001447 3812182.180000 ;
    imh:0001474 4211882.500000 .

However, the serializer fails to use the prefix to abbreviate and uses the full URIs are used:

@prefix imh: <http://ontology.mil/foundry/IMH_> .

<urn:uuid0442f858-1c1b-4031-8e03-8ed8aba08b22>
    <http://ontology.mil/foundry/IMH_0001430> 4229807.310000 ;
    <http://ontology.mil/foundry/IMH_0001447> 3799718.720000 ;
    <http://ontology.mil/foundry/IMH_0001474> 4215095.780000 .

The abbreviation fails when the first character after the colon is a digit.