load_weights error

[stytim]

Traceback (most recent call last):
File "test.py", line 63, in
model.load_weights('weights/weights_CONCAT.hdf5')
File "/home/tianyu/anaconda3/envs/pp/lib/python2.7/site-packages/keras/engine/topology.py", line 2398, in load_weights
layer_names = [n.decode('utf8') for n in f.attrs['layer_names']]
File "h5py/_objects.pyx", line 54, in h5py._objects.with_phil.wrapper
File "h5py/_objects.pyx", line 55, in h5py._objects.with_phil.wrapper
File "/home/tianyu/anaconda3/envs/pp/lib/python2.7/site-packages/h5py/_hl/attrs.py", line 60, in getitem
attr = h5a.open(self._id, self._e(name))
File "h5py/_objects.pyx", line 54, in h5py._objects.with_phil.wrapper
File "h5py/_objects.pyx", line 55, in h5py._objects.with_phil.wrapper
File "h5py/h5a.pyx", line 77, in h5py.h5a.open
KeyError: "Can't open attribute (can't locate attribute: 'layer_names')"

I am using Keras 1.0.6. What could cause this problem?