--- uim/slib.c
+++ uim/slib.c
@@ -2924,6 +2924,14 @@
   mark_protected_registers ();
   mark_locations ((LISP *) stack_start_ptr,
 		  (LISP *) & stack_end);
+#ifdef __ia64__
+  {
+    extern void *__libc_ia64_register_backing_store_base;
+    __builtin_ia64_flushrs ();
+    mark_locations ((LISP *) __libc_ia64_register_backing_store_base,
+		    (LISP *) __builtin_ia64_bsp ());
+  }
+#endif
   gc_sweep ();
   gc_ms_stats_end ();
 }