Ottava dash-fraction = #0.0 produces dots, not "no line"

[Knute Snortum]

>I'm not top posting

The section on the 2.18 version of OttavaBracket...

http://www.lilypond.org/doc/v2.18/Documentation/internals/ottavabracket

...looks like this:

  dash-fraction (number):
    0.3
    Size of the dashes, relative to dash-period. Should be between 0.0 (no
line) and 1.0 (continuous line).

But this code...
%% --- Start
\version "2.18.2"

\relative c,, {
  \clef bass
  \ottava #-1
  \override Staff.OttavaBracket.dash-fraction = #0.0
  c4 c c c
}
%% --- End

...produces a dotted line, not "no line" as the documentations states.
 Either the documentation or the behavior should be changed.

Knute Snortum
(via Gmail)