diff --git a/examples/mixture-tpe.py b/examples/mixture-tpe.py
index 754d02e66..ba3ba23c5 100644
--- a/examples/mixture-tpe.py
+++ b/examples/mixture-tpe.py
@@ -283,7 +283,8 @@ def my_write_viz(step, t, state, dv, exact=None, resid=None):
             exact = initializer(x_vec=nodes, eos=eos, time=t)
         if resid is None:
             resid = state - exact
-        viz_fields = [("cv", state), ("dv", dv)]
+        viz_fields = [("cv", state), ("dv", dv),
+                      ("resid", resid), ("exact", exact)]
         from mirgecom.simutil import write_visfile
         write_visfile(dcoll, viz_fields, visualizer, vizname=casename,
                       step=step, t=t, overwrite=True, vis_timer=vis_timer,
@@ -356,7 +357,7 @@ def my_pre_step(step, t, dt, state):
             if do_viz:
                 if exact is None:
                     exact = initializer(x_vec=nodes, eos=eos, time=t)
-                resid = state - exact
+                resid = fluid_state.cv - exact
                 my_write_viz(step=step, t=t, state=cv, dv=dv, exact=exact,
                              resid=resid)
 
diff --git a/examples/mixture.py b/examples/mixture.py
index e6d4e0e70..f6276615d 100644
--- a/examples/mixture.py
+++ b/examples/mixture.py
@@ -277,7 +277,8 @@ def my_write_viz(step, t, state, dv, exact=None, resid=None):
             exact = initializer(x_vec=nodes, eos=eos, time=t)
         if resid is None:
             resid = state - exact
-        viz_fields = [("cv", state), ("dv", dv)]
+        viz_fields = [("cv", state), ("dv", dv),
+                      ("resid", resid), ("exact", exact)]
         from mirgecom.simutil import write_visfile
         write_visfile(dcoll, viz_fields, visualizer, vizname=casename,
                       step=step, t=t, overwrite=True, vis_timer=vis_timer,
@@ -350,7 +351,7 @@ def my_pre_step(step, t, dt, state):
             if do_viz:
                 if exact is None:
                     exact = initializer(x_vec=nodes, eos=eos, time=t)
-                resid = state - exact
+                resid = fluid_state.cv - exact
                 my_write_viz(step=step, t=t, state=cv, dv=dv, exact=exact,
                              resid=resid)
 
diff --git a/mirgecom/fluid.py b/mirgecom/fluid.py
index 6c3ddff59..7f1b5e32b 100644
--- a/mirgecom/fluid.py
+++ b/mirgecom/fluid.py
@@ -272,6 +272,8 @@ def replace(self, **kwargs):
         from dataclasses import replace
         return replace(self, **kwargs)
 
+    __array_ufunc__ = None
+
 
 def _aux_shape(ary, leading_shape):
     """:arg leading_shape: a tuple with which ``ary.shape`` is expected to begin."""
diff --git a/mirgecom/wall_model.py b/mirgecom/wall_model.py
index d243e2dc6..ea97486a2 100644
--- a/mirgecom/wall_model.py
+++ b/mirgecom/wall_model.py
@@ -105,6 +105,8 @@ def array_context(self):
         """Return an array context for the :class:`SolidWallConservedVars` object."""
         return get_container_context_recursively(self.mass)
 
+    __array_ufunc__ = False
+
 
 @dataclass_array_container
 @dataclass(frozen=True, eq=False)