qt4_editor/formlayout.py TypeError: float() argument must be a string or a number

Using matplotlib 1.2 within pyqt on Python 3.3 I receive

formlayout.py", line 343, in get
    value = float(field.text())
TypeError: float() argument must be a string or a number

That does not happen under Python 2.7.
Modifying that line in backends/qt4_editor/formlayout.py by wrapping the field.text() into a str() like

value = float(str(field.text()))

solves this.