diff --git a/gc/gc.h b/gc/gc.h
index 8ca9987..89219eb 100644
--- a/gc/gc.h
+++ b/gc/gc.h
@@ -96,6 +96,8 @@ MODULAR_GC_FN bool rb_memerror_reentered(void);
 MODULAR_GC_FN bool rb_obj_id_p(VALUE);
 MODULAR_GC_FN void rb_gc_before_updating_jit_code(void);
 MODULAR_GC_FN void rb_gc_after_updating_jit_code(void);
+MODULAR_GC_FN bool rb_gc_obj_shareable_p(VALUE);
+MODULAR_GC_FN void rb_gc_rp(VALUE);
 
 #if USE_MODULAR_GC
 MODULAR_GC_FN bool rb_gc_event_hook_required_p(rb_event_flag_t event);
diff --git a/gc/mmtk/mmtk.c b/gc/mmtk/mmtk.c
index 9dd3129..5861f5e 100644
--- a/gc/mmtk/mmtk.c
+++ b/gc/mmtk/mmtk.c
@@ -1260,6 +1260,12 @@ rb_gc_impl_copy_attributes(void *objspace_ptr, VALUE dest, VALUE obj)
     rb_gc_impl_copy_finalizer(objspace_ptr, dest, obj);
 }
 
+bool
+rb_gc_impl_checking_shareable(void *ptr)
+{
+    return false;
+}
+
 // GC Identification
 
 const char *