diff --git a/folx/ad.py b/folx/ad.py
index 6e06fc0..0b39b2c 100644
--- a/folx/ad.py
+++ b/folx/ad.py
@@ -9,6 +9,30 @@ def is_tree_complex(tree):
     return any(jnp.iscomplexobj(leaf) for leaf in leaves)
 
 
+def _varying_axes(x: jax.Array) -> tuple:
+    if not hasattr(jax, 'typeof'):
+        return ()
+
+    typ = jax.typeof(x)
+    manual_axis_type = getattr(typ, 'manual_axis_type', None)
+    if manual_axis_type is not None:
+        return tuple(getattr(manual_axis_type, 'varying', ()))
+
+    return tuple(getattr(typ, 'vma', ()))
+
+
+def _mark_varying_like(x: jax.Array, like: jax.Array) -> jax.Array:
+    axes = _varying_axes(like)
+    if not axes:
+        return x
+
+    if hasattr(jax.lax, 'pcast'):
+        return jax.lax.pcast(x, axes, to='varying')
+    if hasattr(jax.lax, 'pvary'):
+        return jax.lax.pvary(x, axes)
+    return x
+
+
 def vjp_rc(fun, *primals: jax.Array):
     def real_fun(*primals):
         return jnp.real(fun(*primals))
@@ -72,8 +96,7 @@ def flat_f(x):
         out = flat_f(flat_primals)
 
         eye = jnp.eye(out.size, dtype=out.dtype)
-        if hasattr(jax.lax, 'pvary'):
-            eye = jax.lax.pvary(eye, tuple(jax.typeof(out).vma))
+        eye = _mark_varying_like(eye, out)
         result = jax.vmap(vjp(flat_f, flat_primals))(eye)[0]
         result = jax.vmap(unravel, out_axes=0)(result)
         if len(primals) == 1:
@@ -94,8 +117,7 @@ def jvp_fun(s):
             return jax.jvp(f, primals, unravel(s))[1]
 
         eye = jnp.eye(flat_primals.size, dtype=flat_primals.dtype)
-        if hasattr(jax.lax, 'pvary'):
-            eye = jax.lax.pvary(eye, tuple(jax.typeof(flat_primals).vma))
+        eye = _mark_varying_like(eye, flat_primals)
         J = jax.vmap(jvp_fun, out_axes=-1)(eye)
         return J