The farmer in the what?

Lately Tyler has really gotten into singing the song, The Farmer in the Dell. Only he doesn't say dell, he says hell.

The farmer in the hell,
the farmer in the hell,
hi! ho! the dairy-o,
the farmer in the hell.

I try to correct him, without drawing too much attention to the word. I'm afraid that if I make a big deal about it, it'll be worse and he'll do it on purpose. Every once in a while, (after reminding him) he'll sing it right. But then later he'll slip up and resort back to his preferred version.

I have to admit though, the song is a lot funnier his way.