Error in lily-library.scm with 2.15.14

[Nick Payne]

I have one score that when when I try to build it with 2.15.14, I get 
the following output in the log.

===============================================
Processing `/home/nick/lilypond/chaconne.ly'
Parsing...
Interpreting music... 
[8][16][24][32][40][48][56][64][72][80][88][96][104][112][120][128][136][144][152][160][168][176][184][192][200][208][216][224][232][240][248][256]
Preprocessing graphical objects...
Interpreting music... 
/usr/local/lilypond/usr/share/lilypond/current/scm/lily-library.scm:210:5: 
In procedure ly:book-process in expression (process-procedure book paper 
...):
/usr/local/lilypond/usr/share/lilypond/current/scm/lily-library.scm:210:5: 
Wrong type (expecting exact integer): -1.0
===============================================

I don't get this error with any of the other scores I have built with 
2.15.14, and this score built without error on 2.14 and hasn't been 
modified since except by running convert-ly against it.

I copied the score across to a Windows machine with 2.14.2 installed, 
changed the \version statement back to 2.14.2, and it built without any 
error. The machine with 2.15.14 installed is running Ubuntu amd64.

Nick