gcc compile time error with cimport_from_pyx

[c-f-h]

The following setup with 2 pyx files and the corresponding setup.py to build them results in a gcc compile time error:

#>>> moda.pyx

cdef class ClassA:
    cdef int[2] a

#>>> modb.pyx

from moda cimport ClassA

cdef class ClassB(ClassA):
    cdef int[2] b

#>>> setup.py

from setuptools import setup
from Cython.Build import cythonize
import Cython.Compiler.Options

Cython.Compiler.Options.cimport_from_pyx = True

setup(
        ext_modules = cythonize(["moda.pyx", "modb.pyx"],
            compiler_directives={'language_level': 3})
)

The error is as follows:

$ python setup.py build
running build
running build_ext
building 'modb' extension
gcc -pthread -B /home/clemens/miniconda3/compiler_compat -Wl,--sysroot=/ -Wsign-compare -DNDEBUG -g -fwrapv -O3 -Wall -Wstrict-prototypes -fPIC -I/home/clemens/miniconda3/include/python3.7m -c modb.c -o build/temp.linux-x86_64-3.7/modb.o
modb.c:2585:32: error: redefinition of ‘__Pyx_carray_to_py_int’
 static CYTHON_INLINE PyObject *__Pyx_carray_to_py_int(int *__pyx_v_v, Py_ssize_t __pyx_v_length) {
                                ^~~~~~~~~~~~~~~~~~~~~~
modb.c:2038:32: note: previous definition of ‘__Pyx_carray_to_py_int’ was here
 static CYTHON_INLINE PyObject *__Pyx_carray_to_py_int(int *__pyx_v_v, Py_ssize_t __pyx_v_length) {
                                ^~~~~~~~~~~~~~~~~~~~~~
modb.c:2696:32: error: redefinition of ‘__Pyx_carray_to_tuple_int’
 static CYTHON_INLINE PyObject *__Pyx_carray_to_tuple_int(int *__pyx_v_v, Py_ssize_t __pyx_v_length) {
                                ^~~~~~~~~~~~~~~~~~~~~~~~~
modb.c:2149:32: note: previous definition of ‘__Pyx_carray_to_tuple_int’ was here
 static CYTHON_INLINE PyObject *__Pyx_carray_to_tuple_int(int *__pyx_v_v, Py_ssize_t __pyx_v_length) {
                                ^~~~~~~~~~~~~~~~~~~~~~~~~
modb.c:2804:12: error: redefinition of ‘__Pyx_carray_from_py_int’
 static int __Pyx_carray_from_py_int(PyObject *__pyx_v_o, int *__pyx_v_v, Py_ssize_t __pyx_v_length) {
            ^~~~~~~~~~~~~~~~~~~~~~~~
modb.c:2257:12: note: previous definition of ‘__Pyx_carray_from_py_int’ was here
 static int __Pyx_carray_from_py_int(PyObject *__pyx_v_o, int *__pyx_v_v, Py_ssize_t __pyx_v_length) {
            ^~~~~~~~~~~~~~~~~~~~~~~~
error: command 'gcc' failed with exit status 1

The issue seems to be that certain utility functions are getting inserted into the C source file multiple times. The error goes away if cimport_from_pyx is disabled and a moda.pxd file is generated manually.

This is Python 3.7.4, Cython 0.29.20, Linux (WSL) with gcc 7.5.0.