Stock Historical Bars - Error when requesting interval more than 5minutes

Firstly, it was incredibly frustrating to find how to request historical bar data for a period other than Day. Through various posts showing outdated syntax I was able to piece it together. Every single example uses timeframe=TimeFrame.Day.

On to the issue. When I try to get 15 minute data I get the following error:

raise APIError(error, http_error)
alpaca.common.exceptions.APIError: {"message":"timeframe period number is larger than the allowed maximum of 59"}

The timeframe entry of this code generates the error:
request_params = StockBarsRequest(
symbol_or_symbols=tickers,
timeframe=TimeFrame(amount=15, unit=TimeFrame.Minute),
start=start_date,
end=end_date
)

However, when I use the same format but replace 15 with 5, it works. Anything above 5 results in the same error. The 59 indicates to me that it thinks that I am using the Minute time unit to request periods above an hour, but 15 is obviously below 59. Any help is appreciated! Thanks

Thank you