When using the GNU coreutils split command with verbose mode, how can I make the lines that appear in the STDOUT be flushed with respect to the time when the file has finally been created?

Fore example, running it like this:

~/coreutils/bin/split --verbose -d -u -l 10000000 1>out & tail -f out
creating file `x00'
creating file `x01'
creating file `x02'
[...]

I would have expected the line creating file 'x00' to have appeared in file out after the file has been completely written, but instead, it seems like nothing is written into out until the whole file has been finally processed. Is there a way to change this behavior?