Dynamodb Update Error Invalid Updateexpression: an Expression Attribute Value Used in Expression Is Not Defined

I am trying to perform an update on DynamoDB table.

The code is (Node.js):

    let params = {
        TableName: Organizations.Table,
        Key: {
            'ID': event.ID
        },
        UpdateExpression: 'SET #OrgName = :org, #Description = :desc',
        ExpressionAttributeNames: {
            '#OrgName': 'OrgName',
            '#Description': 'Description'
        },
        ExpressionAtributeValues: {
            ':org': event.OrgName,
            ':desc': event.Description
        },
        ReturnValues: 'UPDATED_NEW'
    };
    this.docClient.update(params, (err, data) => {
        if (err) {
            return cb(err);
        }
        return cb(null, data);
    });

The event object has all the properties needed.

After executing I get an error:

Invalid UpdateExpression: An expression attribute value used in expression is not defined; attribute value: :desc

I just followed the examples from DynamoDB docs. When I change the order of set values, e.g. to SET #Description = :desc, #OrgName = :org the error I get will be about attribute value :org. I also tried to specify expression attribute values explicitly, didn't help.

I can't get what is wrong.

Can someone help me?