Loading an example from the welcome screen results in warning: "Project is part of Qt sources that do not match the Qt defined in the kit"

I have installed Qt Creator beta2 using the online installer. When I load an example from the welcome screen and use a Qt version that matches the one from the example a warning icon appears next to the project in project view. Its tooltip is: "Warning: Project is part of Qt sources that do not match the Qt defined in the kit"