Cannot get data for YM e-mini micro from IB

I know the format for the YM e-mini for IB is:

YM^^^MAR^21-ECBOT-FUT (where each ^ is a space)

Using ECBOT-FUT-USD on the end part will also work.

But to get the micro contract, I was expecting this to work:

MYM^^^MAR^21-ECBOT-FUT-USD (also tried this)

The IB plugin is reporting that this symbol is invalid. I have no trouble getting the MES, M2K and MNQ micro contracts (different symbol format, of course).

I'm using 6.39.0.

Thanks for showing me the error of my ways.

The answer is already in this thread post #42: How to find correct IB symbol using TWS