Forgot to include supporting form in tax return - what now?

I just filed my (individual) tax return and forgot to include form 8936 supporting the $2500 tax credit for a plug-in prius we purchased last year. I claimed the $2500 on the 1040, so the amount we owe (and paid with the return) was correct, I just forgot to attach the supporting form. Do I just wait for the IRS to contact me (and presumably deny the credit), or is there a way to send in the supporting form now and have it associated with the return to avoid the hassle? Its not exactly an amended return because nothing on the actual return changes, just an addendum to include the supporting form they require.