checking if jsonb was detoasted and releasing memory

Let us say that the datum of type Datum contains a Jsonb* type.
Then after the call

Jsonb *jb = DatumGetJsonb(datum);

the jb might point to a palloc'ed structure, in case detoasting took place.
So the question is if this is the right way to free up the memory after
checking that the jb was detoasted?

if ((void *)jb != DatumGetPointer(datum))
pfree(jb); // free if detoasted