Bigquery add columns to table schema

I am trying to add new column to BigQuery existing table. I have tried bq command tool and API approach. I get following error when making call to Tables.update().

I have tried with providing full schema with additional field and that also gives me same error as shown below.

With API I get following Error:

{
    "schema": {
        "fields": [{
            "name": "added_column",
            "type": "integer",
            "mode": "nullable"
        }]
    }
}



{
    "error": {
        "errors": [{
            "domain": "global",
            "reason": "invalid",
            "message": "Provided Schema does not match Table [blah]"
        }],
        "code": 400,
        "message": "Provided Schema does not match Table [blah]"
    }
}

With BQ tool I get following error:

./bq update -t blah added_column:integer

BigQuery error in update operation: Provided Schema does not match Table [blah]