spin giving the error: error, the version of spin that generated this pan.c assumed a different wordsize (4 iso 8) even if both 64 bit

Question

I am trying to use verification with the spin model checker.

I am using the 64-bit version of spin using the spin651_windows64 binary. Together with the 64 bit of cygwin.

And yet when I try to do

spin -a ex_1a.pml (the exercises from the spin model checker website)
gcc -o pan pan.c
pan.exe

I'm getting the error

spin: error, the version of spin that generated this pan.c assumed a different wordsize (4 iso 8)