PySide doesn't find QML plugin by default

I'm trying to use Kirigami (https://kde.org/products/kirigami/) in my PySide project. In my QML file im using

import org.kde.kirigami 2.0 as Kirigami

When starting the app (python main.py) I get

qml/main.qml:3 module "org.kde.kirigami" is not installed

Running 'QML2_IMPORT_PATH=/usr/lib/qt/qml python main.py' works fine

Running a C++/QML app with Kirigami works fine without the additional env variable.

PySide is installed via pip. When installing it from the Manjaro packages it works fine without the env variable.

Kirigami is installed from the Manjaro packages.