error save model

[vvssttkk]

I fitted my model

topic_model = ct.Corex(n_hidden=50, words=words, max_iter=300, verbose=1, seed=1)
topic_model.fit(doc_word, words=words)

after I want to save her: topic_model.save(filename='./model/corex.dat') and getting the error::

---------------------------------------------------------------------------
OSError                                   Traceback (most recent call last)
<timed eval> in <module>

~/env/py36/lib/python3.6/site-packages/corextopic/corextopic.py in save(self, filename)
    490         if path.dirname(filename) and not path.exists(path.dirname(filename)):
    491             makedirs(path.dirname(filename))
--> 492         pickle.dump(self, open(filename, 'wb'), protocol=-1)
    493         # Restore words to CorEx object
    494         self.words = temp_words

OSError: [Errno 22] Invalid argument

Haw fix this problem?