diff --git a/tket/test/src/test_GreedyPauli.cpp b/tket/test/src/test_GreedyPauli.cpp
index 4fd630369d..b5db4dfdd5 100644
--- a/tket/test/src/test_GreedyPauli.cpp
+++ b/tket/test/src/test_GreedyPauli.cpp
@@ -831,15 +831,18 @@ SCENARIO("Test GreedyPauliSimpMT") {
             0.125)),
         {0, 1, 2, 3, 4, 5});
 
-    Circuit d(circ);
-    d.decompose_boxes_recursively();
+    Circuit d0(circ);
+    d0.decompose_boxes_recursively();
+    Circuit d1(d0);
     REQUIRE(Transforms::multi_thread_greedy_pauli_optimisation(
                 3, 0.7, 0.3, 500, 500, 0, true, 100)
-                .apply(d));
+                .apply(d0));
+
     REQUIRE(Transforms::multi_thread_greedy_pauli_optimisation(
                 3, 0.7, 0.3, 500, 500, 0, false, 100)
-                .apply(d));
-    REQUIRE(test_unitary_comparison(circ, d, true));
+                .apply(d1));
+    REQUIRE(test_unitary_comparison(circ, d0, true));
+    REQUIRE(test_unitary_comparison(circ, d1, true));
   }
 }