warning: 'cbyeditor' undefined in chicago-notes

[AlistairK]

I have been trying to fix a problem with a BibLaTeX run using the
chicago-notes style. The document has bold 'cbyeditor' as a
place-holder. The log file says

> Package biblatex Warning: Bibliography string 'cbyeditor' undefined

The following line is in cms-american.lbx

> cbyeditor = {{\cbytypeeditor}{\cbytypeeditor}}

I found a mention of this problem on a Norwegian forum where it went
unanswered, but Google turned up nothing from comp.text.tex.

Any help would be appreciated.

[AlistairK]

I just found out that this error occurs only when called as
\usepackage[style=chicago-notes-df]{biblatex}, but not when called as
\usepackage{biblatex-chicago}.