diff -up clisp-2.49.93/src/record.d.alias clisp-2.49.93/src/record.d
--- clisp-2.49.93/src/record.d.alias	2018-02-26 11:40:53.668845947 -0500
+++ clisp-2.49.93/src/record.d	2018-02-26 11:41:22.225164509 -0500
@@ -1539,7 +1539,7 @@ global maygc object update_instance (obj
         ptr->inst_class_version = obj;
         clr_break_sem_1(); /* permit interrupts again */
       }
-      ASSERT(Record_flags(STACK_(2+4+2*kept_slots)) & instflags_forwarded_B);
+      ASSERT(record_flags(TheInstance(STACK_(2+4+2*kept_slots))) & instflags_forwarded_B);
       dotimesL(kept_slots,kept_slots, {
         var object new_slotinfo = popSTACK();
         ASSERT(atomp(new_slotinfo));