diff --git a/shape.c b/shape.c
index 608dc71da3..20ff0d305b 100644
--- a/shape.c
+++ b/shape.c
@@ -930,12 +930,6 @@ rb_shape_get_iv_index(shape_id_t shape_id, ID id, attr_index_t *value)
     return true;
 }
 
-void
-rb_shape_set_shape(VALUE obj, rb_shape_t *shape)
-{
-    rb_shape_set_shape_id(obj, rb_shape_id(shape));
-}
-
 int32_t
 rb_shape_id_offset(void)
 {
diff --git a/shape.h b/shape.h
index ef6c868896..017a27ef15 100644
--- a/shape.h
+++ b/shape.h
@@ -130,7 +130,6 @@ bool rb_shape_id_too_complex_p(shape_id_t shape_id);
 bool rb_shape_has_object_id(rb_shape_t *shape);
 bool rb_shape_id_has_object_id(shape_id_t shape_id);
 
-void rb_shape_set_shape(VALUE obj, rb_shape_t *shape);
 shape_id_t rb_shape_transition_frozen(VALUE obj);
 shape_id_t rb_shape_transition_complex(VALUE obj);
 shape_id_t rb_shape_transition_remove_ivar(VALUE obj, ID id, shape_id_t *removed_shape_id);