Deductions & credits

I am a US citizen. Have been abroad (living in Israel) for many years, am employed in Israel and paid in Israeli currency to an Israeli bank account, and I pay taxes in Israel. For US tax purposes, I had used the conversion rate on 12/31/18 to enter the dollar amounts, but then came across something related to Form 1116 that said if I am converting foreign taxes paid in foreign currency I cannot use TT Online. Is this the case? Thank you for your response.