Time change breaks the layout

[Noeck]

Hi,

while testing some snippets, I encountered a strange behaviour in the
following code:

\version "2.16.0" % "2.17.14" as well
{
  a1 \break
  \time 3/4  % fine without time change
  a1 \break
  %\time 6/8 % "6/8" is also at an ugly position
  %a2.
}

The barline is not at the end of the second line but well before. The
\time 6/8, that can be commented in, is also much too far from the
preceding bar line. I agree that this is spaced-out extremely wide but
LilyPond could do much better, nonetheless.
Is this a bug?

Cheers,
Joram