diff --git a/src/gc.c b/src/gc.c
index a6ff0c588..b0885a307 100644
--- a/src/gc.c
+++ b/src/gc.c
@@ -448,6 +448,7 @@ mrb_gc_destroy(mrb_state *mrb, mrb_gc *gc)
 static void
 gc_protect(mrb_state *mrb, mrb_gc *gc, struct RBasic *p)
 {
+  if (is_red(p)) return;
 #ifdef MRB_GC_FIXED_ARENA
   if (gc->arena_idx >= MRB_GC_ARENA_SIZE) {
     /* arena overflow error */