diff --git a/xla/python/sharding.cc b/xla/python/sharding.cc
index d9d509cd95a5bc..0779618d5454b9 100644
--- a/xla/python/sharding.cc
+++ b/xla/python/sharding.cc
@@ -182,6 +182,9 @@ NamedSharding::NamedSharding(nb::object mesh, nb::object spec,
       parsed_pspec_(std::move(parsed_pspec)),
       manual_axes_(std::move(manual_axes)),
       logical_device_ids_(std::move(logical_device_ids)) {
+  if (spec_.is_none()) {
+    throw nb::type_error("Unexpected None passed as spec_ for NamedSharding.");
+  }
   nb::object idl = nb::object(mesh_.attr("_internal_device_list"));
   if (idl.is_none()) {
     internal_device_list_ = std::nullopt;
diff --git a/xla/python/xla_client.py b/xla/python/xla_client.py
index eaa783ccb4005a..430d3d8c35fedb 100644
--- a/xla/python/xla_client.py
+++ b/xla/python/xla_client.py
@@ -50,7 +50,7 @@
 
 # Just an internal arbitrary increasing number to help with backward-compatible
 # changes. In JAX, reference this via jax._src.lib.xla_extension_version.
-_version = 305
+_version = 306
 
 # Version number for MLIR:Python components.
 mlir_api_version = 57