'errorCode': 'invalid.request.timeInForce' when using Python

[SharesFTW]

Hi does anyone know why this error occurs? I can open up a trade if ordertype is set to market, however recent experience has forced me to explore using a limit approach to opening positions as the IG API returns loss making opening positions that do not correspond with the streaming index values.  My API trading parameters are as follows:

{'epic': 'IX.D.FTSE.DAILY.IP'

'expiry': 'DFB'

'direction': 'SELL'

'size': '1'

'orderType': 'LIMIT'

'timeInForce': 'FILL_OR_KILL'

'level': '6200'

'guaranteedStop': 'false'

'stopLevel': None

'stopDistance': '7'

'forceOpen': 'true'

'limitLevel': None

'limitDistance': '3'

'quoteId': None

'currencyCode': 'GBP'}   any help would be much appreciated Thanks