homebrew-osgeo4mac: conflicting version recursive dependencies during upgrade

Hi,

I was trying to upgrade my qgis2 installation and it fails with the following error:

brew upgrade qgis2 --with-globe --with-grass --with-isolation --with-orfeo5 --with-qspatialite --with-r --with-saga-gis --with-qspatialite --with-saga-gis-lts
==> Upgrading 1 outdated package, with result:
osgeo/osgeo4mac/qgis2 2.18.11_1
Error: osgeo/osgeo4mac/qgis2 contains conflicting version recursive dependencies:
  qwt-qt4, qwt-qt4@5.2

Not sure what this means…any ideas?