Windows: AWS CLI works except for "aws sts get-caller-identity"

I have set up a static key pair and get the following error on Windows 10, I have tried the latest as well as a slightly older version. My profile works fine on a Mac::

$ aws sts get-caller-identity --profile foo

Unable to parse response (no element found: line 1, column 0), invalid XML received. Further retries may succeed: b''

File "awscli\botocore\parsers.py", line 243, in parse File "awscli\botocore\parsers.py", line 533, in _do_error_parse File "awscli\botocore\parsers.py", line 482, in _parse_xml_string_to_dom botocore.parsers.ResponseParserError: Unable to parse response (no element found: line 1, column 0), invalid XML received. Further retries may succeed: b''

Unable to parse response (no element found: line 1, column 0), invalid XML received. Further retries may succeed: b''

Other CLI commands work fine:

$ aws s3 ls 2017-11-27 22:46:10 config-bucket-108...

Any idea what might cause this? Changing the "output" in the config files doesn't work, config is shown below and the same works on a Mac. Any idea???

$ cat config [default] region = us-east-1 output = text [profile foo] region = us-east-1 output = json