diff --git a/docs/api/array.md b/docs/api/array.md
index 265cbd3..47dba50 100644
--- a/docs/api/array.md
+++ b/docs/api/array.md
@@ -95,16 +95,15 @@ BatchImage = Float[Array, "batch channels height width"]
 
 Note that `jaxtyping.{Array, ArrayLike}` are only available if JAX has been installed.
 
-## Scalars, PRNGKeys
+## Scalars, PRNG keys
 
 For convenience, jaxtyping also includes `jaxtyping.Scalar`, `jaxtyping.ScalarLike`, and `jaxtyping.PRNGKeyArray`, defined as:
 ```python
 Scalar = Shaped[Array, ""]
 ScalarLike = Shaped[ArrayLike, ""]
 
-# Depending on the value of `JAX_ENABLE_CUSTOM_PRNG`:
-PRNGKeyArray = Key[Array, ""]
-PRNGKeyArray = UInt32[Array, "2"]
+# Left: new-style typed keys; right: old-style keys. See JEP 9263.
+PRNGKeyArray = Union[Key[Array, ""], UInt32[Array, "2"]]
 ```
 
 Recalling that shape-and-dtype specified jaxtyping arrays can be nested, this means that e.g. you can annotate the output of `jax.random.split` with `Shaped[PRNGKeyArray, "2"]`, or e.g. an integer scalar with `Int[Scalar, ""]`.
diff --git a/jaxtyping/_array_types.py b/jaxtyping/_array_types.py
index 8113829..91f0878 100644
--- a/jaxtyping/_array_types.py
+++ b/jaxtyping/_array_types.py
@@ -657,12 +657,10 @@ Num = _make_dtype(uints + ints + floats + complexes, "Num")
 Shaped = _make_dtype(_any_dtype, "Shaped")
 
 if has_jax:
-    if jax.config.jax_enable_custom_prng:
-        _key_regex = re.compile(r"^key<\w+>$")
-        Key = _make_dtype(_key_regex, "Key")
-        PRNGKeyArray = Key[jax.Array, ""]
-    else:
-        Key = UInt32
-        PRNGKeyArray = Key[jax.Array, "2"]
+    _key_regex = re.compile(r"^key<\w+>$")
+    Key = _make_dtype(_key_regex, "Key")
+    # New-style `jax.random.key` have scalar shape and dtype `key<foo>`.
+    # Old-style `jax.random.PRNGKey` have shape `(2,)` and dtype `uint32`.
+    PRNGKeyArray = Union[Key[jax.Array, ""], UInt32[jax.Array, "2"]]
     Scalar = Shaped[jax.Array, ""]
     ScalarLike = Shaped[jax.typing.ArrayLike, ""]