2 files changed, 4 insertions, 1 deletions
diff --git a/gc/default/default.c b/gc/default/default.c
index 1b45d4b724..5664b3dd90 100644
--- a/gc/default/default.c
+++ b/gc/default/default.c
@@ -6006,9 +6006,10 @@ rb_gc_impl_writebarrier(void *objspace_ptr, VALUE a, VALUE b)
 
     if (RGENGC_CHECK_MODE) {
         if (SPECIAL_CONST_P(a)) rb_bug("rb_gc_writebarrier: a is special const: %"PRIxVALUE, a);
-        if (SPECIAL_CONST_P(b)) rb_bug("rb_gc_writebarrier: b is special const: %"PRIxVALUE, b);
     }
 
+    if (SPECIAL_CONST_P(b)) return;
+
     GC_ASSERT(RB_BUILTIN_TYPE(a) != T_NONE);
     GC_ASSERT(RB_BUILTIN_TYPE(a) != T_MOVED);
     GC_ASSERT(RB_BUILTIN_TYPE(a) != T_ZOMBIE);
diff --git a/gc/mmtk/mmtk.c b/gc/mmtk/mmtk.c
index 41e7f13972..9e4ee9f3de 100644
--- a/gc/mmtk/mmtk.c
+++ b/gc/mmtk/mmtk.c
@@ -750,6 +750,8 @@ rb_gc_impl_writebarrier(void *objspace_ptr, VALUE a, VALUE b)
 {
     struct MMTk_ractor_cache *cache = rb_gc_get_ractor_newobj_cache();
 
+    if (SPECIAL_CONST_P(b)) return;
+
     mmtk_object_reference_write_post(cache->mutator, (MMTk_ObjectReference)a);
 }