mypy fails with mypyc, even with empty file

Steps to reproduce:

• pip install mypy # that's 0.740 here, also same with HEAD on github
• pip install mypy-mypyc
• create an empty file foo.py

mypy foo.py

Traceback (most recent call last):
  File "/home/xo/.conda/envs/intel37/bin/mypy", line 6, in <module>
    from mypy.__main__ import console_entry
  File "/home/xo/.conda/envs/intel37/lib/python3.7/site-packages/mypy/__main__.py", line 4, in <module>
    from mypy.main import main
  File "mypy/main.py", line 12, in <module>
  File "/home/xo/.conda/envs/intel37/lib/python3.7/site-packages/mypy/build.py", line 33, in <module>
    from mypy.semanal import SemanticAnalyzer
  File "/home/xo/.conda/envs/intel37/lib/python3.7/site-packages/mypy/semanal.py", line 84, in <module>
    from mypy.messages import best_matches, MessageBuilder, pretty_or
  File "/home/xo/.conda/envs/intel37/lib/python3.7/site-packages/mypy/messages.py", line 28, in <module>
    from mypy.typetraverser import TypeTraverserVisitor
  File "mypy/typetraverser.py", line 14, in <module>
SystemError: null argument to internal routine

This combination may seem weird but the traceback is not helping much when this happens...