If a person does not know that Zakat al-Fitr should be given in the form of common food items and instead…

If a person does not know that Zakat al-Fitr should be given in the form of common food items and instead gives cash, believing it to be Zakat al-Fitr without intending it as a substitute, and without the intention of substituting it for the value of the food, but rather thinking that the cash itself is Zakat al-Fitr out of ignorance of the rule, does it suffice or not?