\bar causes line break

[Kieren Richard MacMillan]

[ Lilypond 2.8.1 ]

Hello, all --

I have

    \time 6/8
    \partial 8*3 s4.
    s2.*10
    \time 5/8
    s4. \bar ":" s4
    s4 \bar ":" s4.

Unfortunately, at this measure, I get a line-break (see attached  
screenshot).

I tried \noBreak, to \noAvail...  ;-)

Any thoughts? Is this expected behaviour?

Thanks,
Kieren.