Segmentation fault in QtCreator 3.3.0 from 5.4.0 RC on Kubuntu/KDE5

Trying to start QtCreator on Kubuntu Utopic/KDE5 results in segfault.
Backtrace:
Starting program: /home/forger/Qt5.4.0/Tools/QtCreator/bin/qtcreator
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib/x86_64-linux-gnu/libthread_db.so.1".
[New Thread 0x7fffed4eb700 (LWP 6317)]

Program received signal SIGSEGV, Segmentation fault.
0x00007ffff6b911eb in QVariant::~QVariant() () from /home/forger/Qt5.4.0/Tools/QtCreator/bin/../lib/qtcreator/libQt5Core.so.5
(gdb) bt
#0 0x00007ffff6b911eb in QVariant::~QVariant() () from /home/forger/Qt5.4.0/Tools/QtCreator/bin/../lib/qtcreator/libQt5Core.so.5
#1 0x00007ffff5366c72 in QGuiApplicationPrivate::init() () from /home/forger/Qt5.4.0/Tools/QtCreator/bin/../lib/qtcreator/./libQt5Gui.so.5
#2 0x00007ffff74707b2 in QApplication::QApplication(int&, char**, int) () from /home/forger/Qt5.4.0/Tools/QtCreator/bin/../lib/qtcreator/libQt5Widgets.so.5
#3 0x000000000040b129 in ?? ()
#4 0x0000000000406a2c in ?? ()
#5 0x00007ffff5d8dec5 in __libc_start_main (main=0x406980, argc=1, argv=0x7fffffffe1c8, init=<optimized out>, fini=<optimized out>, rtld_fini=<optimized out>, stack_end=0x7fffffffe1b8) at libc-start.c:287
#6 0x000000000040a985 in ?? ()
#7 0x00007fffffffe1b8 in ?? ()
#8 0x000000000000001c in ?? ()
#9 0x0000000000000001 in ?? ()
#10 0x00007fffffffe599 in ?? ()
#11 0x0000000000000000 in ?? ()

Even if the plugin is incompatible with current Qt version some error message is more preferable than segfault.

Overriding QT_PLUGIN_PATH doesn't seem to fix the problem.