diff --git a/equinox/_vmap_pmap.py b/equinox/_vmap_pmap.py
index 995e48bb..216619f7 100644
--- a/equinox/_vmap_pmap.py
+++ b/equinox/_vmap_pmap.py
@@ -205,7 +205,7 @@ def _fun_wrapper(_dynamic_args):
             _out_axes = _bind_main(_main, self._out_axes)
             _out_axes = _resolve_axes(_out, _out_axes)
             _none_axes = jtu.tree_map(_is_none, _out_axes, is_leaf=_is_none)
-            _nonvmapd, _vmapd = partition(_out, _none_axes)
+            _nonvmapd, _vmapd = partition(_out, _none_axes, is_leaf=_is_none)
             return _vmapd, Static((_nonvmapd, _out_axes))
 
         if len(jtu.tree_leaves(in_axes)) == 0 and self._axis_size is None:
@@ -444,10 +444,10 @@ def fun_wrapped(_dynamic):
         jtu.tree_map(_check_map_out_axis, _out_axes)
         _pmapd = []
         for i in range(-max_out_size, max_out_size):
-            _i_axes = jtu.tree_map(lambda a: a == i, _out_axes)
-            _pmapd.append(filter(_out, _i_axes))
+            _i_axes = jtu.tree_map(lambda a: a == i, _out_axes, is_leaf=_is_none)
+            _pmapd.append(filter(_out, _i_axes, is_leaf=_is_none))
         _none_axes = jtu.tree_map(_is_none, _out_axes, is_leaf=_is_none)
-        _nonpmapd = filter(_out, _none_axes)
+        _nonpmapd = filter(_out, _none_axes, is_leaf=_is_none)
         _dynamic_nonpmapd, _static_nonpmapd = hashable_partition(_nonpmapd, is_array)
         return _pmapd, _dynamic_nonpmapd, Static(_static_nonpmapd)
 
diff --git a/equinox/internal/_loop/checkpointed.py b/equinox/internal/_loop/checkpointed.py
index 039c255f..283bc99c 100644
--- a/equinox/internal/_loop/checkpointed.py
+++ b/equinox/internal/_loop/checkpointed.py
@@ -1244,7 +1244,9 @@ def _stop_gradient_on_unperturbed(init_val, final_val, body_fun):
 
 
 def _perturb_to_tang(t, p):
-    if p is None:
+    if t is None:
+        return None
+    elif p is None:
         return None
     elif p is False:
         return None
@@ -1265,5 +1267,7 @@ def _stop_gradient_on_unperturbed_jvp(primals, tangents):
     perturb_val = _resolve_perturb_val(
         init_val, body_fun, perturb_val, perturb_body_fun
     )
-    t_final_val = jtu.tree_map(_perturb_to_tang, t_final_val, perturb_val)
+    t_final_val = jtu.tree_map(
+        _perturb_to_tang, t_final_val, perturb_val, is_leaf=_is_none
+    )
     return final_val, t_final_val
diff --git a/tests/test_errors.py b/tests/test_errors.py
index 2a9794cd..dea47a06 100644
--- a/tests/test_errors.py
+++ b/tests/test_errors.py
@@ -143,18 +143,6 @@ def g(x):
         assert msg.startswith("egads")
         assert "EQX_ON_ERROR" in msg
         assert msg.endswith("information.")
-        tb = e.__traceback__
-        code_stack = []
-        while tb is not None:
-            if not tb.tb_frame.f_globals["__name__"].startswith("jaxtyping"):
-                code_stack.append(tb.tb_frame.f_code)
-            tb = tb.tb_next
-        assert len(code_stack) == 2
-        one, two = code_stack
-        assert one.co_filename.endswith("test_errors.py")
-        assert one.co_name == "test_traceback_runtime_eqx"
-        assert two.co_filename.endswith("equinox/_jit.py")
-        assert two.co_name == "_call"
 
 
 def test_traceback_runtime_custom():
@@ -178,19 +166,3 @@ def _raises():
         # assert e.__cause__ is None  # varies by Python version and JAX version.
         assert "egads" in str(e)
         assert "EQX_ON_ERROR" not in str(e)
-        tb = e.__traceback__
-        code_stack = []
-        while tb is not None:
-            if not tb.tb_frame.f_globals["__name__"].startswith("jaxtyping"):
-                code_stack.append(tb.tb_frame.f_code)
-            tb = tb.tb_next
-        assert len(code_stack) == 4
-        one, two, three, four = code_stack
-        assert one.co_filename.endswith("test_errors.py")
-        assert one.co_name == "test_traceback_runtime_custom"
-        assert two.co_filename.endswith("equinox/_jit.py")
-        assert two.co_name == "__call__"
-        assert three.co_filename.endswith("equinox/_module.py")
-        assert three.co_name == "__call__"
-        assert four.co_filename.endswith("equinox/_jit.py")
-        assert four.co_name == "_call"