Error: Trendline command: invalid Trendline period for 'sma(count)'

[maverick]

I am running the following search in the Splunk Search GUI:

* daysago=30  |timechart count| trendline sma(count)as thecount

and I am receiving an error in red that says the trendline has an invalid trendline period for argument 'sma(count)'

Does anyone know what this means and, hopefully, how to correct?

[Paolo_Prigione]

Shouldn't that be

sma5(count) 

with 5 (or other) being the window used for the average?