QJsonDocument toJson(QJsonDocument::Compact) not working

[ChrisW67]

That looks like your program is finding a Qt 5.0 library at run time (its version of toJson() does not take an argument). Use ldd in the same environment that the program is being run to determine what libraries it will try to load.

[elmar.wieser]

That's correct. I found the problem. I'm running the application on a remote system. This remote system was on Qt 5.0.2 and this has only toJson() without arguments.