StateVector.read with dtype raises AttributeError

The following example raises an AttributeError because the dtype kwarg isn't handled well (from ldas-pcdev2.ligo.caltech.edu):

>>> from gwpy.timeseries import StateVector
>>> StateVector.read('/archive/frames/ER7/hoft/H1/H-H1_HOFT_C00-11181/H-H1_HOFT_C00-1118183424-4096.gwf', 'H1:ODC-MASTER_CHANNEL_OUT_DQ', dtype='uint32')
---------------------------------------------------------------------------
AttributeError                            Traceback (most recent call last)
... snip ...
/home/duncan.macleod/.local/lib/python2.6/site-packages/gwpy-0.1b1.dev118-py2.6.egg/gwpy/timeseries/io/gwf/framecpp.pyc in _read_frame(framefile, channels, ctype, dtype, verbose, _SeriesClass)
    267         ts = None
    268         i = 0
--> 269         dtype_ = dtype.get(channel, None)
    270         while True:
    271             try:

AttributeError: 'NoneType' object has no attribute 'get'