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https://github.com/pydata/xarray/issues/4898#issuecomment-778312719 https://api.github.com/repos/pydata/xarray/issues/4898 778312719 MDEyOklzc3VlQ29tbWVudDc3ODMxMjcxOQ== 367900 2021-02-12T16:55:11Z 2021-02-12T16:55:11Z CONTRIBUTOR

grepping the code, the only other function that calls _maybe_null_out is prod, and I can confirm the problem also exists there. Updated the title, MCVE for prod:

```python import numpy as np import xarray as xr

def worker(da): if da.shape == (0, 0): return da

raise RuntimeError("I was evaluated")

da = xr.DataArray( np.random.normal(size=(20, 500)), dims=("x", "y"), coords=(np.arange(20), np.arange(500)), )

da = da.chunk(dict(x=5)) lazy = da.map_blocks(worker) result1 = lazy.prod("x", skipna=True) result2 = lazy.prod("x", skipna=True, min_count=5) ```

 
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