diff --git a/pyiceberg/table/update/__init__.py b/pyiceberg/table/update/__init__.py
index 2f0e6c13d2..c30d960d38 100644
--- a/pyiceberg/table/update/__init__.py
+++ b/pyiceberg/table/update/__init__.py
@@ -21,9 +21,9 @@
 from abc import ABC, abstractmethod
 from datetime import datetime
 from functools import singledispatch
-from typing import TYPE_CHECKING, Annotated, Any, Dict, Generic, List, Literal, Optional, Set, Tuple, TypeVar, Union, cast
+from typing import TYPE_CHECKING, Annotated, Any, Dict, Generic, List, Literal, Optional, Tuple, TypeVar, Union, cast
 
-from pydantic import Field, field_validator, model_validator
+from pydantic import Field, field_validator, model_serializer, model_validator
 
 from pyiceberg.exceptions import CommitFailedException
 from pyiceberg.partitioning import PARTITION_FIELD_ID_START, PartitionSpec
@@ -52,6 +52,8 @@
 from pyiceberg.utils.properties import property_as_int
 
 if TYPE_CHECKING:
+    from pydantic.functional_serializers import ModelWrapSerializerWithoutInfo
+
     from pyiceberg.table import Transaction
 
 U = TypeVar("U")
@@ -727,6 +729,12 @@ class AssertRefSnapshotId(ValidatableTableRequirement):
     ref: str = Field(...)
     snapshot_id: Optional[int] = Field(default=None, alias="snapshot-id")
 
+    @model_serializer(mode="wrap")
+    def serialize_model(self, handler: ModelWrapSerializerWithoutInfo) -> dict[str, Any]:
+        partial_result = handler(self)
+        # Ensure "snapshot-id" is always present, even if value is None
+        return {**partial_result, "snapshot-id": self.snapshot_id}
+
     def validate(self, base_metadata: Optional[TableMetadata]) -> None:
         if base_metadata is None:
             raise CommitFailedException("Requirement failed: current table metadata is missing")
@@ -745,13 +753,6 @@ def validate(self, base_metadata: Optional[TableMetadata]) -> None:
         elif self.snapshot_id is not None:
             raise CommitFailedException(f"Requirement failed: branch or tag {self.ref} is missing, expected {self.snapshot_id}")
 
-    # override the override method, allowing None to serialize to `null` instead of being omitted.
-    def model_dump_json(
-        self, exclude_none: bool = False, exclude: Optional[Set[str]] = None, by_alias: bool = True, **kwargs: Any
-    ) -> str:
-        # `snapshot-id` is required in json response, even if null
-        return super().model_dump_json(exclude_none=False)
-
 
 class AssertLastAssignedFieldId(ValidatableTableRequirement):
     """The table's last assigned column id must match the requirement's `last-assigned-field-id`."""
diff --git a/tests/test_serializers.py b/tests/test_serializers.py
index ad40ea08e0..3f2bd73e48 100644
--- a/tests/test_serializers.py
+++ b/tests/test_serializers.py
@@ -18,7 +18,7 @@
 import json
 import os
 import uuid
-from typing import Any, Dict
+from typing import Any, Dict, Tuple
 
 import pytest
 from pytest_mock import MockFixture
@@ -26,6 +26,8 @@
 from pyiceberg.serializers import ToOutputFile
 from pyiceberg.table import StaticTable
 from pyiceberg.table.metadata import TableMetadataV1
+from pyiceberg.table.update import AssertRefSnapshotId, TableRequirement
+from pyiceberg.typedef import IcebergBaseModel
 
 
 def test_legacy_current_snapshot_id(
@@ -48,3 +50,13 @@ def test_legacy_current_snapshot_id(
     backwards_compatible_static_table = StaticTable.from_metadata(metadata_location)
     assert backwards_compatible_static_table.metadata.current_snapshot_id is None
     assert backwards_compatible_static_table.metadata == static_table.metadata
+
+
+def test_null_serializer_field() -> None:
+    class ExampleRequest(IcebergBaseModel):
+        requirements: Tuple[TableRequirement, ...]
+
+    request = ExampleRequest(requirements=(AssertRefSnapshotId(ref="main", snapshot_id=None),))
+    dumped_json = request.model_dump_json()
+    expected_json = """{"type":"assert-ref-snapshot-id","ref":"main","snapshot-id":null}"""
+    assert expected_json in dumped_json