Jan Vroonhof <vroonhof(a)math.ethz.ch&gt; writes: You are right. Maybe the solution is simply to always store the symbol referenced by a pure structure to Vpure_uninterned_symbol_table. Does uncommenting the "if (!NILP (XSYMBOL (obj)->obarray)) return obj;" part fix your crash? If yes, we should investigate how large the Vpure_uninterned_symbol_table ends up. If not very large, then that's probably a good fix. The "pure space" thing will not exist in 21.2 anyway. The Vpure_uninterned_symbol_table stuff was introduced by Kyle. I thought you referred to that.