[NTG-context] index register justification

Hi, just by chance I found this minimal example and (while showgrid) had a closer look at it: \defineregister[Index][Indeces] \showframe\showgrid \starttext \dorecurse{100}{ boo\Index{boo} Boo\Index{Boo} foo\Index{foo} Foo\Index{Foo} goo\Index{goo} Goo\Index{Goo} \page } \placeregister[Index][align=yes] \stoptext Why are the lines not fully justified? This looks not good, esp. when the entire book is set in justified block! Is this a default that can be changed? Steffen