[Qgis-user] 2.18.0: Dissolve doesn't allow multiple fields

[mvr at posteo.de]

Hi all,

the changelog for 2.18 says that the processing dissolve algorithm now 
allows multiple unique fields 
(http://qgis.org/de/site/forusers/visualchangelog218/index.html#feature-processing-dissolve-algorithm-accepts-multiple-fields). 
I just downloaded and installed the 2.18 version and removed the old 
versions, but the dissolve tool looks the same as before - only one 
unique ID field can be chosen. Are there some files from the older 
QGIS-versions which haven't been removed and now the new tool can't 
load? Or what else can cause this problem?
Thanks for help!

Martin