diff --git a/tests/unit/test_channel_root.py b/tests/unit/test_channel_root.py
index aaa6194..49a9e1f 100644
--- a/tests/unit/test_channel_root.py
+++ b/tests/unit/test_channel_root.py
@@ -13,9 +13,11 @@ from .test_numerical_operators import compile_run
 
 @pytest.mark.parametrize("shift", [0, 1])
 @pytest.mark.parametrize("profile", [0, 1])
-def test_actual_kernel_uniform_parity(tmp_path, shift, profile):
+@pytest.mark.parametrize("clamp,damping", [(1, ".5f"), (0, ".8f")])
+def test_actual_kernel_uniform_parity(tmp_path, shift, profile, clamp, damping):
     """Nonuniform ghosts, corners, top wall, global profile and outlet halo donor."""
-    defines = dict(USE_DDF_SHIFTING=shift, INLET_PROFILE=profile)
+    defines = dict(USE_DDF_SHIFTING=shift, INLET_PROFILE=profile,
+                   OUTLET_BACKFLOW_CLAMP=clamp, OUTLET_SRT_NEQ_DAMP=damping)
     uniform = np.array(compile_run(tmp_path, "channel_root.cpp", dict(
         defines, UNIFORM=1, NX=24, NY=20)), np.float32)
     assert np.isfinite(uniform).all()
diff --git a/tests/validation/multigrid/test_channel_root_gpu.py b/tests/validation/multigrid/test_channel_root_gpu.py
index 80c96e2..5e66415 100644
--- a/tests/validation/multigrid/test_channel_root_gpu.py
+++ b/tests/validation/multigrid/test_channel_root_gpu.py
@@ -82,9 +82,11 @@ class ChannelRootGPU(unittest.TestCase):
     def test_uniform_matched_root(self):
         with CudaContext(0) as context:
             for shifted in (False, True):
-                for profile in ("uniform", "parabolic"):
+                for profile, clamp, damping in (("uniform", True, .5), ("parabolic", True, .5),
+                                                ("parabolic", False, .8)):
                     cfg = LBMConfig(nx=24, ny=20, viscosity=.1, velocity=.025,
-                                    ddf_shifting=shifted, inlet_profile=profile)
+                                    ddf_shifting=shifted, inlet_profile=profile,
+                                    outlet_backflow_clamp=clamp, outlet_srt_neq_damp=damping)
                     initial = _encode_physical(state(cfg.ny, cfg.nx), shifted)
                     expected = run_root(cfg, context, initial)
                     self.assertTrue(np.isfinite(expected).all())