Cannot install some packages with Pacman/Octopi - Suspicious execution method

When installing many packages with Pacman (through Octopi), I get the following error message: > Installing selected packages... > > QApplication: invalid style override 'gtk' passed, ignoring it. > Available styles: Breeze, bb10dark, bb10bright, kvantum-dark, kvantum, > cleanlooks, gtk2, cde, motif, plastique, qt5ct-style, Oxygen, QtCurve, > Windows, Fusion > > octopi-helper[aborted]: Suspicious execution method > > Command finished with errors! It seems to be more a warning than an error, anyway it does not let me install the corresponding package. I use KDE/Qt, but I have most of GTK installed. I looked for a "octopi-helper" package to reinstall it, but could not find it. What else can I try?