html_url,issue_url,id,node_id,user,created_at,updated_at,author_association,body,reactions,performed_via_github_app,issue
https://github.com/pydata/xarray/issues/4543#issuecomment-717436557,https://api.github.com/repos/pydata/xarray/issues/4543,717436557,MDEyOklzc3VlQ29tbWVudDcxNzQzNjU1Nw==,10194086,2020-10-27T18:22:50Z,2020-10-27T18:22:50Z,MEMBER,"I think the problem is in `align` and that `pd.Index([""a""])` has `dtype=object`:

```python
import pandas as pd
pd.Index([""a"", ""b""])
```

`concat` calls `align` here

https://github.com/pydata/xarray/blob/adc55ac4d2883e0c6647f3983c3322ca2c690514/xarray/core/concat.py#L383

and align basically does the following:

```python
index = da1.indexes[""x2""] | da2.indexes[""x2""]
da1.reindex({""x2"": index})
```

Thus we replace the coords with an index.






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