shouldInterruptJavaScript is not called

import sys
import PySide
from PySide import QtCore
from PySide.QtGui import QApplication
from PySide.QtWebKit import QWebPage

print PySide._version_ ## PySide-1.2.2

class QWebPageHeadless(QWebPage):
@QtCore.Slot()
def shouldInterruptJavaScript(self):
print "Interrupt javascript request ignored..."
return False

if _name_ == "_main_":
app = QApplication(sys.argv)
page = QWebPageHeadless()
page.mainFrame().setHtml('<script>while(1);</script>')
sys.exit(app.exec_())

shouldInterruptJavaScript not fired - i see javascript prompt - "javascript problem .... YES/NO"