[igraph] Problems with Pajek file format (node attributes)

[Riccardo Tasso]

Dear all,
    I have the following pajek file, wich I import in R with the usual 
g <- read.graph(filename, 'pajek'):

*vertices 3
1 98 "a"
2 11 "b"
3 38 "c d"
*arcs
1 2 3
2 1 1
3 1 8

Each node has a numeric attribute and a string attribute.
When I serialize my network with graph.write(g, filename, 'pajek'), I 
obtain a strange text file:

*Vertices 3
1 "98" a
2 "11" b
3 "38" c  d
*Arcs
1 2 3
2 1 1
3 1 8

The problem is that without quotes strings with spaces give a parse 
error reading back the last pajek written:

Error in read.graph.pajek(file, ...) :
  At foreign.c:574 : Parse error in Pajek file, line 3 (syntax error), 
Parse error

Is there a way to resolve my problem?
Thank you,
    Riccardo