Given the following code:

\enableregime [utf]
> \mainlanguage [en]
> \definepapersize[sheet][width=1280px, height=960px]
> \setuppapersize[sheet][sheet]
> \setupexternalfigures[directory={img,
>     /home/ubuntu/EGU2016-Presentation,
>     /home/ubuntu/ConTeXt/img}]
> \usemodule[simplefonts]
> \setmainfont[Adventor][expansion=quality,protrusion=quality]
> \setupcolors[state=start]
> \definecolor[faimsblue][h=1B3E93]
> \definecolor[faimsorange][h=F68E1E]
> \setuphead[section][placehead=yes, page=yes, number=no, align=middle,
> style={\setupbodyfont[40pt]}]
>
> \setuplayout[
>     backspace=.01\pagewidth,
>     header=0pt,
>     footer=.02\pageheight,
>     topspace=.185\pageheight,
>     cutspace-.1\pagewidth,
>     width=.87\pagewidth,
>     height=.798\pageheight,
>     bottomspace=.8cm,
>     bottom=12pt
>     ]
> \setuppagenumbering[location=]
> \setupinteraction
>   [page=yes,
>    color=faimsblue,
>    contrastcolor=faimsorange,
>    menu=on,
>    state=start]
> \setupsubpagenumber
>   [way=bytext,
>    state=start]
> \startinteractionmenu[bottom]
> {\interactionbar[alternative=f,width=\makeupwidth,height=2ex]}
> \stopinteractionmenu
> \starttext
> \input knuth
> \section{section 1}
> \input knuth
>
> \section{section 2}
> \input knuth
>
>
> \section{section 3}
> \input knuth
>
>
> \section{section 4}
> \input knuth
> \stoptext


(used in a real presentation:
http://context.fedarch.org/Context/presentation.pdf with environment at
https://github.com/FAIMS/EGU2016-Presentation/blob/master/envpresentation.tex
)

it seems that the interactionmenu doesn't have a button for the final page.
I'm assuming I did something wrong, but I'm not quite sure what it is.