diff --git a/checkpoint/orbax/checkpoint/_src/metadata/checkpoint_test.py b/checkpoint/orbax/checkpoint/_src/metadata/checkpoint_test.py
index d3ae79884..5e33e0405 100644
--- a/checkpoint/orbax/checkpoint/_src/metadata/checkpoint_test.py
+++ b/checkpoint/orbax/checkpoint/_src/metadata/checkpoint_test.py
@@ -140,6 +140,22 @@ def get_metadata_file_path(
     elif metadata_type == RootMetadata:
       return checkpoint.root_metadata_file_path(path or self.directory)
 
+  def assertMetadataEqual(
+      self, a: StepMetadata | RootMetadata, b: StepMetadata | RootMetadata,
+  ):
+    if isinstance(a, StepMetadata):
+      self.assertEqual(a.format, b.format)
+      self.assertEqual(a.item_handlers, b.item_handlers)
+      # ignore item_metadata
+      self.assertEqual(a.metrics, b.metrics)
+      self.assertEqual(a.performance_metrics, b.performance_metrics)
+      self.assertEqual(a.init_timestamp_nsecs, b.init_timestamp_nsecs)
+      self.assertEqual(a.commit_timestamp_nsecs, b.commit_timestamp_nsecs)
+      self.assertEqual(a.custom, b.custom)
+    elif isinstance(a, RootMetadata):
+      self.assertEqual(a.format, b.format)
+      self.assertEqual(a.custom, b.custom)
+
   @parameterized.parameters(True, False)
   def test_read_unknown_path(self, blocking_write: bool):
     self.assertIsNone(
@@ -221,7 +237,7 @@ def test_read_default_values(
     serialized_metadata = self.write_metadata_store(blocking_write).read(
         file_path=self.get_metadata_file_path(metadata_class),
     )
-    self.assertEqual(
+    self.assertMetadataEqual(
         self.deserialize_metadata(metadata_class, serialized_metadata),
         metadata,
     )
@@ -249,7 +265,7 @@ def test_read_with_values(
     serialized_metadata = self.write_metadata_store(blocking_write).read(
         file_path=self.get_metadata_file_path(metadata_class),
     )
-    self.assertEqual(
+    self.assertMetadataEqual(
         self.deserialize_metadata(metadata_class, serialized_metadata),
         metadata,
     )
@@ -296,7 +312,7 @@ def test_update_without_prior_data(
     serialized_metadata = self.write_metadata_store(blocking_write).read(
         file_path=self.get_metadata_file_path(metadata_class),
     )
-    self.assertEqual(
+    self.assertMetadataEqual(
         self.deserialize_metadata(metadata_class, serialized_metadata),
         metadata_class(
             format=_SAMPLE_FORMAT,
@@ -331,7 +347,7 @@ def test_update_with_prior_data(
     serialized_metadata = self.write_metadata_store(blocking_write).read(
         file_path=self.get_metadata_file_path(metadata_class)
     )
-    self.assertEqual(
+    self.assertMetadataEqual(
         self.deserialize_metadata(metadata_class, serialized_metadata),
         metadata_class(
             format=_SAMPLE_FORMAT,
@@ -366,7 +382,7 @@ def test_update_with_unknown_kwargs(
     serialized_metadata = self.write_metadata_store(blocking_write).read(
         file_path=self.get_metadata_file_path(metadata_class)
     )
-    self.assertEqual(
+    self.assertMetadataEqual(
         self.deserialize_metadata(metadata_class, serialized_metadata),
         metadata_class(
             format=_SAMPLE_FORMAT,
@@ -417,7 +433,7 @@ def test_non_blocking_write_request_enables_writes(
     serialized_metadata = self.read_metadata_store(blocking_write=True).read(
         file_path=self.get_metadata_file_path(metadata_class)
     )
-    self.assertEqual(
+    self.assertMetadataEqual(
         self.deserialize_metadata(metadata_class, serialized_metadata),
         self.get_metadata(metadata_class),
     )
@@ -436,14 +452,14 @@ def test_non_blocking_write_request_enables_writes(
     serialized_metadata = self.read_metadata_store(blocking_write=False).read(
         file_path=self.get_metadata_file_path(metadata_class)
     )
-    self.assertEqual(
+    self.assertMetadataEqual(
         self.deserialize_metadata(metadata_class, serialized_metadata),
         self.get_metadata(metadata_class, custom={'a': 2}),
     )
     serialized_metadata = self.write_metadata_store(blocking_write=False).read(
         file_path=self.get_metadata_file_path(metadata_class)
     )
-    self.assertEqual(
+    self.assertMetadataEqual(
         self.deserialize_metadata(metadata_class, serialized_metadata),
         self.get_metadata(metadata_class, custom={'a': 2}),
     )
@@ -457,14 +473,14 @@ def test_non_blocking_write_request_enables_writes(
     serialized_metadata = self.read_metadata_store(blocking_write=False).read(
         file_path=self.get_metadata_file_path(metadata_class)
     )
-    self.assertEqual(
+    self.assertMetadataEqual(
         self.deserialize_metadata(metadata_class, serialized_metadata),
         self.get_metadata(metadata_class, custom={'a': 3}),
     )
     serialized_metadata = self.write_metadata_store(blocking_write=False).read(
         file_path=self.get_metadata_file_path(metadata_class)
     )
-    self.assertEqual(
+    self.assertMetadataEqual(
         self.deserialize_metadata(metadata_class, serialized_metadata),
         self.get_metadata(metadata_class, custom={'a': 3}),
     )
@@ -528,37 +544,6 @@ def test_deserialize_wrong_types_step_metadata(
     with self.assertRaises(ValueError):
       self.deserialize_metadata(StepMetadata, wrong_metadata)
 
-  @parameterized.parameters(
-      (
-          RootMetadata(custom={'a': None}),
-          {'custom': {'a': None}}
-      ),
-      (
-          RootMetadata(format=_SAMPLE_FORMAT),
-          {'format': _SAMPLE_FORMAT}
-      ),
-      (
-          StepMetadata(format=_SAMPLE_FORMAT),
-          {'format': _SAMPLE_FORMAT},
-      ),
-      (
-          StepMetadata(item_handlers={'a': 'a_handler'}),
-          {'item_handlers': {'a': 'a_handler'}},
-      ),
-      (
-          StepMetadata(custom={'blah': 123}),
-          {'custom': {'blah': 123}},
-      ),
-  )
-  def test_only_serialize_non_default_metadata_values(
-      self,
-      metadata: StepMetadata | RootMetadata,
-      expected_serialized_metadata: dict[str, Any],
-  ):
-    self.assertEqual(
-        self.serialize_metadata(metadata), expected_serialized_metadata
-    )
-
   @parameterized.parameters(StepMetadata, RootMetadata)
   def test_unknown_key_in_metadata(
       self, metadata_class: type[StepMetadata] | type[RootMetadata],
diff --git a/checkpoint/orbax/checkpoint/_src/metadata/root_metadata_serialization.py b/checkpoint/orbax/checkpoint/_src/metadata/root_metadata_serialization.py
index 5117a4fbc..05f0e4c84 100644
--- a/checkpoint/orbax/checkpoint/_src/metadata/root_metadata_serialization.py
+++ b/checkpoint/orbax/checkpoint/_src/metadata/root_metadata_serialization.py
@@ -24,12 +24,10 @@
 
 def serialize(metadata: RootMetadata) -> SerializedMetadata:
   """Serializes `metadata` to a dictionary."""
-  serialized_metadata = {}
-  if metadata.format is not None:
-    serialized_metadata['format'] = metadata.format
-  if metadata.custom:
-    serialized_metadata['custom'] = metadata.custom
-  return serialized_metadata
+  return {
+      'format': metadata.format,
+      'custom': metadata.custom,
+  }
 
 
 def deserialize(metadata_dict: SerializedMetadata) -> RootMetadata:
diff --git a/checkpoint/orbax/checkpoint/_src/metadata/step_metadata_serialization.py b/checkpoint/orbax/checkpoint/_src/metadata/step_metadata_serialization.py
index c5c5e4dc4..78d987133 100644
--- a/checkpoint/orbax/checkpoint/_src/metadata/step_metadata_serialization.py
+++ b/checkpoint/orbax/checkpoint/_src/metadata/step_metadata_serialization.py
@@ -47,25 +47,15 @@ def serialize(metadata: StepMetadata) -> SerializedMetadata:
       if isinstance(val, float)
   }
 
-  serialized_metadata = {}
-  if metadata.format is not None:
-    serialized_metadata['format'] = metadata.format
-  if metadata.item_handlers:
-    serialized_metadata['item_handlers'] = metadata.item_handlers
-  if metadata.metrics:
-    serialized_metadata['metrics'] = metadata.metrics
-  if float_metrics:
-    serialized_metadata['performance_metrics'] = float_metrics
-  if metadata.init_timestamp_nsecs is not None:
-    serialized_metadata['init_timestamp_nsecs'] = metadata.init_timestamp_nsecs
-  if metadata.commit_timestamp_nsecs is not None:
-    serialized_metadata['commit_timestamp_nsecs'] = (
-        metadata.commit_timestamp_nsecs
-    )
-  if metadata.custom:
-    serialized_metadata['custom'] = metadata.custom
-
-  return serialized_metadata
+  return {
+      'format': metadata.format,
+      'item_handlers': metadata.item_handlers,
+      'metrics': metadata.metrics,
+      'performance_metrics': float_metrics,
+      'init_timestamp_nsecs': metadata.init_timestamp_nsecs,
+      'commit_timestamp_nsecs': metadata.commit_timestamp_nsecs,
+      'custom': metadata.custom,
+  }
 
 
 def deserialize(
@@ -87,6 +77,8 @@ def deserialize(
     validated_metadata_dict['item_handlers'] = item_handlers
   elif isinstance(item_handlers, CheckpointHandlerTypeStr):
     validated_metadata_dict['item_handlers'] = item_handlers
+  elif item_handlers is None:
+    validated_metadata_dict['item_handlers'] = None
 
   utils.validate_field(metadata_dict, 'item_metadata', [dict, str])
   dict_item_metadata = metadata_dict.get('item_metadata')