kwant.continuum test failure with Sympy 1.3

>>> import kwant
>>> import sympy
>>> kwant.__version__
'1.4.0a0.dev66+gd2145780'
>>> sympy.__version__
'1.3'
>>> kwant.test()
=============================================== test session starts ================================================
platform linux -- Python 3.6.1, pytest-3.8.0, py-1.5.2, pluggy-0.7.1 -- /home/jbw/.local/miniconda/bin/python
cachedir: .pytest_cache
rootdir: /home/jbw/work/code/2014/kwant, inifile:
plugins: timeit-0.3.0, flakes-2.0.0, cov-2.5.1, hypothesis-3.26.0
collected 221 items / 1 errors                                                                                     

====================================================== ERRORS ======================================================
________ ERROR collecting .local/miniconda/lib/python3.6/site-packages/kwant/continuum/tests/test_common.py ________
.local/miniconda/lib/python3.6/site-packages/kwant/continuum/tests/test_common.py:31: in <module>
    ('k_x * A(x) * k_x', kx * com_A(x_op) * kx),
E   TypeError: 'Symbol' object is not callable
!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!! Interrupted: 1 errors during collection !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!
============================================= 1 error in 0.65 seconds ==============================================
2

Sympy 1.3 was released on conda forge 6 days ago.

I think this blocks the release of 1.4