Text from decrescendo spanner not kept inside line

[Jay Anderson]

Below the "sempre dim." isn't kept inside the line. Shouldn't this be
taken into account? The workaround of course is to put a manual
\noBreak in.

-----Jay

\version "2.11.49"

\score
{
  \new Staff \relative c'
  {
    \override Score.PaperColumn #'keep-inside-line = ##t
    \override Score.NonMusicalPaperColumn #'keep-inside-line = ##t
    \repeat unfold 10 c1 |
    \set decrescendoText = \markup {\italic "sempre dim."}
    \set decrescendoSpanner = #'text
    \override DynamicTextSpanner #'style = #'dashed-line
    c4 c c c\> | \break
    \repeat unfold 10 c1 |
    c1\! |
  }
}