Jan Vroonhof <vroonhof(a)math.ethz.ch&gt; writes: If the vector is in pure space, then all its symbol contents should be interned in Vpure_uninterned_symbol_table until the end of time, and GCPRO'ed through that. If that doesn't happen, it's a bug in the whatever code produces the pure compiled function. As far as I can tell from scanning the code, it's correct: DEFUN ("make-byte-code", Fmake_byte_code, 4, MANY, 0, [...] if (purify_flag) { [...] /* Statistics are kept differently for the constants */ if (!purified (f->constants)) { f->constants = Fpurecopy (f->constants); } This Fpurecopy() should intern the symbols to Vpure_uninterned_symbol_table. You mean Kyle? If you unintern it later, it doesn't matter, because you still have a living reference in Vpure_uninterned_symbol_table, which should keep the GC sweeper from putting its greasy hands on the symbol.