diff -r 2f1798c65fd6 -r c4e394a9c84c src/operator_arithmetic.rs
--- a/src/operator_arithmetic.rs	Mon Sep 01 00:04:22 2025 -0500
+++ b/src/operator_arithmetic.rs	Mon Sep 01 13:51:03 2025 -0500
@@ -2,7 +2,7 @@
 Arithmetic of [`Mapping`]s.
  */
 
-use crate::instance::{Instance, Space};
+use crate::instance::{ClosedSpace, Instance, Space};
 use crate::mapping::{DifferentiableImpl, DifferentiableMapping, Mapping};
 use crate::types::*;
 use serde::Serialize;
@@ -63,7 +63,7 @@
     F: Float,
     D: Space,
     T: DifferentiableMapping<D, DerivativeDomain = V>,
-    V: Space + std::ops::Mul<F, Output = V>,
+    V: ClosedSpace + std::ops::Mul<F, Output = V>,
     C: Constant<Type = F>,
 {
     type Derivative = V;