diff --git a/variable.c b/variable.c
index 1e6367e3c5..e9735a8c4d 100644
--- a/variable.c
+++ b/variable.c
@@ -1752,6 +1752,7 @@ iterate_over_shapes_with_callback(rb_shape_t *shape, rb_ivar_foreach_callback_fu
       case SHAPE_T_OBJECT:
         return iterate_over_shapes_with_callback(rb_shape_get_parent(shape), callback, itr_data);
       case SHAPE_OBJ_TOO_COMPLEX:
+      default:
         rb_bug("Unreachable");
     }
 }