Jan Vroonhof <vroonhof(a)math.ethz.ch&gt; writes: This has been fixed long ago. See Fpurecopy(): /* Order of subsequent tests determined via profiling. */ else if (SYMBOLP (obj)) { /* Symbols can't be made pure (and thus read-only), because assigning to their function, value or plist slots would produced a SEGV in the dumped XEmacs. So we previously would just return the symbol unchanged. But purified aggregate objects like lists and vectors can contain uninterned symbols. If there are no other non-pure references to the symbol, then the symbol is not protected from garbage collection because the collector does not mark the contents of purified objects. So to protect the symbols, an impure reference has to be kept for each uninterned symbol that is referenced by a pure object. All such symbols are stored in the hash table pointed to by Vpure_uninterned_symbol_table, which is itself staticpro'd. */ if (NILP (XSYMBOL (obj)->obarray)) Fputhash (obj, Qnil, Vpure_uninterned_symbol_table); return obj; }