Using the "extra natural" accidental at the beginning of a measure.

[Seth]

Hello. In this snippet

\relative c'' {
\key a \major
b fisis gis a % 1
fis a eis fis % 2
}

I'd like the F-sharp at the beginning of the second measure to be printed with 
both a natural and a sharp sign in acknowledgement of the F double-sharp in the 
previous measure. How could I go about doing this? 

Thanks and regards,