1. I built Qt 5.2 from stable branch ( 7e2e8cad6636584f1d3fc9d213363e5fc6243ef2 ) in a shadow build directory.
2. Using this Qt, I built Creator from 3.0 branch ( d33f7fd2c7ff9410a2619601e2bbf7251e28d1dd ) in a shadow build directory.
3. With this Creator, I created a new Qt Quick 2 Application project and configured it with a kit using the Qt version from step 1.
4. When I switch to Design mode, Creator shows a message box stating that: "The executable of the QML Puppet process (/home/qtrob/dev/bin/qt-5-stable/qtbase/bin/qml2puppet) cannot be started. Please check your installation. QML Puppet is a process which runs in the background to render the items."

The said file exists but is empty. Both Qt's and Creator's directories are writable for the current user.