sort -g (generic numeric) is working only for the first key

[Wasim Akram S.N.]

Hi,
I don't know whether the following is really a bug.

address@hidden:~/temp$ cat a
1    1    1
10    10    10
2    2    2
4    100    100
4    10    10
4    1    1
4    2    2
100    10    1
200    20    100
200    2    10
200    1    1000
address@hidden:~/temp$ sort -g -k1,3 -t \t a
1    1    1
2    2    2
4    100    100
4    10    10
4    1    1
4    2    2
10    10    10
100    10    1
200    1    1000
200    20    100
200    2    10


But my expected output is

1    1    1
2    2    2
4    1    1
4    2    2
4    10    10
4    100    100
etc

Thanks,
Wasim Akram S.N.