gregorian.ly causes failure

I tried to add a score in raw mode, so that it is treated like a file. On my PC it compiles absolutely fine, but in Wikipedia I get the following errors:

`/usr/share/lilypond/2.18.2/ly/gregorian.ly:14:1: error: unrecognized string, not in text script or \lyricmode

IJ = \lyricmode { IJ }
/usr/share/lilypond/2.18.2/ly/gregorian.ly:14:4: error: syntax error, unexpected '='
IJ 
   = \lyricmode { IJ }`

Since the errors a recognized inside gregorian.ly, I guess, it is not related to my document.