diff --git a/chex/_src/asserts.py b/chex/_src/asserts.py
index 6c08c21..99d6eff 100644
--- a/chex/_src/asserts.py
+++ b/chex/_src/asserts.py
@@ -1060,10 +1060,15 @@ def _assert_fn(path, leaf):
 # This is for backwards compatibility.
 def _check_sharding(x):
   if hasattr(jax, "Array") and isinstance(x, jax.Array):
-    if not jax.typeof(x).sharding.is_fully_replicated:
-      return True
+    # Use x.sharding directly for concrete arrays.
+    sharding = getattr(x, "sharding", None)
+    if sharding is not None:
+      return not sharding.is_fully_replicated or len(sharding.device_set) > 1
     else:
-      return len(x.sharding.device_set) > 1
+      # Fallback for backward compatibility.
+      # Many older JAX versions or specific tracers might still need jax.typeof.
+      sharding = jax.typeof(x).sharding
+      return not sharding.is_fully_replicated or len(sharding.device_set) > 1
   # pytype: disable=attribute-error
   return (
       hasattr(jax, "pxla")
@@ -1130,16 +1135,16 @@ def _assert_fn(path, leaf):
                   f" on {leaf_device}."
               )
           else:
-            errors.append((
+            errors.append(
                 f"Tree leaf '{_ai.format_tree_path(path)}' resides "
                 f"on {leaf.devices()} (CPU devices are disallowed)."
-            ))
+            )
         else:
           # Not a jax.Array.
-          errors.append((
+          errors.append(
               f"Tree leaf '{_ai.format_tree_path(path)}' has "
               f"unexpected type: {type(leaf)}."
-          ))
+          )
 
   for path, leaf in jax.tree_util.tree_flatten_with_path(tree)[0]:
     _assert_fn(_ai.convert_jax_path_to_dm_path(path), leaf)
@@ -1183,27 +1188,31 @@ def _assert_fn(path, leaf):
       # Check that the leaf is a DeviceArray.
       if isinstance(leaf, jax.Array):
         if _check_sharding(leaf):
-          errors.append((f"Tree leaf '{_ai.format_tree_path(path)}' is a "
-                         f"ShardedDeviceArray which are disallowed. "
-                         f" (type={type(leaf)})."))
+          errors.append(
+              f"Tree leaf '{_ai.format_tree_path(path)}' is a "
+              f"sharded JAX array (historically ShardedDeviceArray) "
+              f"which are disallowed. (type={type(leaf)})."
+          )
         else:  # DeviceArray and not ShardedDeviceArray
           # Check the platform.
           leaf_device = list(leaf.devices())[0]
           if leaf_device.platform not in platform:
-            errors.append((
+            errors.append(
                 f"Tree leaf '{_ai.format_tree_path(path)}' resides on "
                 f"'{leaf_device.platform}', expected '{platform}'."
-            ))
+            )
 
           # Check the device.
           if device is not None and leaf.devices() != {device}:
-            errors.append((
+            errors.append(
                 f"Tree leaf '{_ai.format_tree_path(path)}' resides on "
                 f"{leaf.devices()}, expected {device}."
-            ))
+            )
       else:
-        errors.append((f"Tree leaf '{_ai.format_tree_path(path)}' has "
-                       f"unexpected type: {type(leaf)}."))
+        errors.append(
+            f"Tree leaf '{_ai.format_tree_path(path)}' has "
+            f"unexpected type: {type(leaf)}."
+        )
 
   for path, leaf in jax.tree_util.tree_flatten_with_path(tree)[0]:
     _assert_fn(_ai.convert_jax_path_to_dm_path(path), leaf)