diff -r ca53a962106c -r 2c76df38d02b src/linops.rs
--- a/src/linops.rs	Mon Dec 30 09:37:34 2024 -0500
+++ b/src/linops.rs	Mon Dec 30 11:00:12 2024 -0500
@@ -371,7 +371,7 @@
     fn apply_mut<I : Instance<Pair<U, V>>>(&self, y : &mut Y, x : I) {
         let Pair(u, v) = x.decompose();
         self.0.apply_mut(y, u);
-        self.1.apply_mut(y, v);
+        self.1.apply_add(y, v);
     }
 
     /// Computes `y += Ax`, where `A` is `Self`