[NTG-context] Again: LuaTeX error: invalid escape sequence near '\i'

An example which was working with ConText (version beginning 2012) - and now I get an error: \define\imagepath {/home/janis/images} \starttext \externalfigure[\imagepath/test.jpg] \stoptext LuaTeX error [string "\directlua "]:1: invalid escape sequence near '\i' Without my parameter \imagepath there ist no problem. And if I want to see the "echo" of the parameter with \imagepath I get "/home/janis/images" which I expect. I need parameters very often. How can I use my parameter \imagepath in \externafigure? Regards Janis