grep bug/inconsistency

[David Liang]

Hi, regarding these two options:
       -n, --line-number
              Prefix each line of output with the line number within its
input file.
       -o, --only-matching
              Show only the part of a matching line that matches PATTERN.

If there are multiple matches on a line, the -o option prints each match on
a separate line, but the line number prefix is printed only for the first
match (I'm running GNU grep 2.5.1).
For example, `grep -no "[fb][oa][or]" afile' gives me this:

30:foo
bar
far
31:boo
for
32:foo
...

Thanks for your attention.