Quick question regarding Generation Transaction

[DannyHamilton]

I'm pretty sure I recall there being a requirement added for a miner (or solo or pool) to put something specific in the input portion of the generation transaction to prevent an issue that came up where two different generation transactions in two different block heights both used the same output script and therefore had identical transaction hashes.  Unfortunately, I can't seem to remember exactly what it is that is supposed to be added to make the transaction unique, and a quick search on Google isn't turning it up.

Am I remembering incorrectly?  Or can someone tell me what it is that's supposed to be added?
 

[PrimeNumber7]

According to Peter Wuille, as of when BIP 34 was implemented, coinbase transactions must have the block height encoded in the previous script (along with potentially additional arbitrary data, although the additional arbitrary data is not required).

[DannyHamilton]

According to Peter Wuille, as of when BIP 34 was implemented, coinbase transactions must have the block height encoded in the previous script (along with potentially additional arbitrary data, although the additional arbitrary data is not required).

Block height! That's it.  Thanks.  Slipped my mind, and I just couldn't seem to remember it.  Thanks!!