diff --git a/test/test_fortran.py b/test/test_fortran.py
index f493550446a27097d524555b523132f0a9d7c4e3..4117b80a27b243dee1db94b5a0bb2b83b2ec8d49 100644
--- a/test/test_fortran.py
+++ b/test/test_fortran.py
@@ -408,6 +408,10 @@ def test_fuse_kernels(ctx_factory):
 
     assert len(knl.temporary_variables) == 2
 
+    # This is needed for correctness, otherwise ordering could foul things up.
+    knl = lp.temporary_to_subst(knl, "prev")
+    knl = lp.temporary_to_subst(knl, "prev_0")
+
     ctx = ctx_factory()
     lp.auto_test_vs_ref(xyderiv, ctx, knl, parameters=dict(nelements=20, ndofs=4))