AssertionError when attempting to import keras related to backend

So, when attempting to import keras, the following AssertionError appears:

    /home/m7nz/anaconda3/envs/ninja-01/lib/python3.6/site-packages/keras/backend/__init__.py in <module>()
     32     assert isinstance(_epsilon, float)
     33     _backend = _config.get('backend', _BACKEND)
---> 34     assert _backend in {'theano', 'tensorflow'}
     35     _image_data_format = _config.get('image_data_format',
     36                                      image_data_format())

AssertionError: 

keras.json is as follows:

{
"floatx": "float32",
"epsilon": 1e-07,
"backend": "theanos",
"image_data_format": "channels_last"

I've tried deleting the reference to tensorflow in the init.py file, but the error remains.

It's on a Linux machine, running ubuntu 16. Using Anaconda3. It's actually in an anaconda environment.

Thank you for your help.