that's one on me

Idioms and Phrases

That's a joke at my expense, as in And after all that discussion they didn't show up—that's one on me . This phrase must be distinguished from that's a new one on me , which means “this is the first time I've heard of or seen that” (as in A checkerboard rug—that's a new one on me ). Both idioms can be used with other personal pronouns (for example, that's one on you ) and date from the early 1900s.