Related על גיטין 107:2

One who eats pure terumah pays from pure chullin (unconsecrated produce). If he paid from impure chullin, what Summachos says is, [if] it is inadvertent, his payment is [valid] payment, [and if it is] intentional, his payment is not [valid] payment. But the Sages say, whether inadvertent or intentional, his payment [of impure produce] is [valid] payment, and [then] he goes back and pays [again] from the pure produce.