How Do I Get TurboTax to Register the After-Tax Contribution to My 401K Rolled Over to Roth IRA (a so-called "Mega Back Door Roth Contribution")?

TurboTax is not registering my after-tax contribution to my I-401K-Regular.

 

My I-401K was empty.

I put $10,919 in as an "employer", after-tax, contribution.   I have an LLC with pass through taxation to me individually so I paid income tax on this amount prior to its contribution.

 

Now when I try to enter my 1099-R which Vanguard provided, I cannot get TurboTax to register the after-tax contribution.

 

On my 1099-G

1.  My Box 1 Gross Distribution is $10919

2.  My Box 2a Taxable Amount is $10919 ( Vanguard says they have to list it this way because they don't keep track of whether "Employer contributions" are post-tax or pre-tax.  Very frustrating.)

3.  Box 5 is empty (Again, Vanguard says they have to list it this way for the reason above).

4.  Box 7 is G

 

When I enter it into TurboTax, TurboTax asks:

 

1. Was this money rolled over to a Roth IRA?   I say "yes".

2.  Did I make after-tax contributions to my 401K?   I say "yes".

3.  A screen comes up asking the list the amount of the after-tax contribution?  I enter "$10,919".

 

But it still assesses me tax as though the rollover was of a pre-tax contribution.  

 

It thus appears not to be registering that the after-tax contribution should register as non-taxable in the rollover to Roth.

 

How do I get it to register that this is after-tax funds and thus should not be taxed again?