Text Spanner on first note after line break

[Jonathan Wilkes]

Hello,
     Can anyone tell me what's going on in the following snippet?  I want 
"a tempo" to be printed above the first note after the line break, but 
it's getting printed at the end of the 1st staff.
     Am I doing something wrong?

Thanks,
Jonathan

\version "2.12.2"

\relative c' {
        \once \override TextSpanner #'(bound-details left text) = #"accel"
        \once \override TextSpanner #'(bound-details right text) = #"a tempo"
        c\startTextSpan d e f \break |
        c\stopTextSpan d e f |
}