In 1.18 (#10151), this will fail with the somewhat clearer AssertionError: assert <class 'numpy.int32'> == <class 'numpy.intc'>. The docstrings perhaps clarify what is going on a little:

In [14]: import inspect

In [15]: print(inspect.getdoc(np.int32))
Signed integer type, compatible with Python `int` anc C ``long``.
Character code: ``'l'``.
Canonical name: ``np.int_``.
Alias *on this platform*: ``np.int32``: 32-bit signed integer (-2147483648 to 2147483647).

In [16]: print(inspect.getdoc(np.intc))
Signed integer type, compatible with C ``int``.
Character code: ``'i'``.

If there is a bug here, it is probably that somewhere in your computation, an np.int_ got replaced with an np.intc, which is inconsistent. If you can trace that down, then we could consider fixing it.

Thanks, I'll look into this.

#10151 is merged, so this can be closed - the error message will be clear.