Possible bug - specifying category messes up coercion?

edit

The snippet

D = CombinatorialFreeModule(ZZ, [1,2])
D(0)

works fine, however

C = CombinatorialFreeModule(ZZ, [1,2], category=AlgebrasWithBasis(ZZ))
C(0)

gets into an infinite loop:

File "/opt/sagemath-9.0/local/lib/python3.7/site-packages/sage/categories/magmas.py", line 488, in one
return self(1)
File "sage/structure/parent.pyx", line 900, in sage.structure.parent.Parent.__call__ (build/cythonized/sage/structure/parent.c:9218)
return mor._call_(x)
File "sage/categories/map.pyx", line 1694, in sage.categories.map.FormalCompositeMap._call_ (build/cythonized/sage/categories/map.c:11607)
x = f._call_(x)
File "sage/categories/morphism.pyx", line 549, in sage.categories.morphism.SetMorphism._call_ (build/cythonized/sage/categories/morphism.c:8489)
cpdef Element _call_(self, x):
File "sage/categories/morphism.pyx", line 568, in sage.categories.morphism.SetMorphism._call_ (build/cythonized/sage/categories/morphism.c:8439)
return self._function(x)
File "/opt/sagemath-9.0/local/lib/python3.7/site-packages/sage/categories/unital_algebras.py", line 70, in from_base_ring
return self.one()._lmul_(r)
File "sage/misc/cachefunc.pyx", line 2310, in sage.misc.cachefunc.CachedMethodCallerNoArgs.__call__ (build/cythonized/sage/misc/cachefunc.c:12712)
self.cache = f(self._instance)

Why is this? Is this expected behaviour?