1 files changed, 1 insertions, 1 deletions
diff --git a/object.c b/object.c
index b420f49067..26c03075a0 100644
--- a/object.c
+++ b/object.c
@@ -135,7 +135,7 @@ rb_class_allocate_instance(VALUE klass)
     RUBY_ASSERT(rb_shape_get_shape(obj)->type == SHAPE_ROOT);
 
     // Set the shape to the specific T_OBJECT shape.
-    ROBJECT_SET_SHAPE_ID(obj, (shape_id_t)(rb_gc_size_pool_id_for_size(size) + 1));
+    ROBJECT_SET_SHAPE_ID(obj, (shape_id_t)(rb_gc_size_pool_id_for_size(size) + FIRST_T_OBJECT_SHAPE_ID));
 
 #if RUBY_DEBUG
     RUBY_ASSERT(!rb_shape_obj_too_complex(obj));