diff --git a/src/key_value/aio/_utils/serialization.py b/src/key_value/aio/_utils/serialization.py
index 91f6e392..40d46c50 100644
--- a/src/key_value/aio/_utils/serialization.py
+++ b/src/key_value/aio/_utils/serialization.py
@@ -76,9 +76,9 @@ def load_dict(self, data: dict[str, Any]) -> ManagedEntry:
         if self._date_format in ("isoformat", "datetime"):
             expected_type = str if self._date_format == "isoformat" else datetime
             parser = parse_datetime_str if self._date_format == "isoformat" else (lambda value: value)
-            if created_at := key_must_be(data, key="created_at", expected_type=expected_type):
+            if (created_at := key_must_be(data, key="created_at", expected_type=expected_type)) is not None:
                 managed_entry_proto["created_at"] = parser(created_at)
-            if expires_at := key_must_be(data, key="expires_at", expected_type=expected_type):
+            if (expires_at := key_must_be(data, key="expires_at", expected_type=expected_type)) is not None:
                 managed_entry_proto["expires_at"] = parser(expires_at)
 
         if "value" not in data:
diff --git a/tests/utils/test_serialization.py b/tests/utils/test_serialization.py
index 2001e849..c789a160 100644
--- a/tests/utils/test_serialization.py
+++ b/tests/utils/test_serialization.py
@@ -3,6 +3,7 @@
 import pytest
 from inline_snapshot import snapshot
 
+from key_value.aio.errors import DeserializationError
 from key_value.aio._utils.managed_entry import ManagedEntry
 from key_value.aio._utils.serialization import BasicSerializationAdapter
 
@@ -80,3 +81,9 @@ def test_entry_two(self, adapter: BasicSerializationAdapter):
 
         assert adapter.load_dict(data=adapter.dump_dict(entry=TEST_ENTRY_TWO)) == snapshot(TEST_ENTRY_TWO)
         assert adapter.load_json(json_str=adapter.dump_json(entry=TEST_ENTRY_TWO)) == snapshot(TEST_ENTRY_TWO)
+
+    @pytest.mark.parametrize("field", ["created_at", "expires_at"])
+    def test_rejects_empty_isoformat_datetime(self, adapter: BasicSerializationAdapter, field: str) -> None:
+        payload = {"value": {"x": 1}, field: ""}
+        with pytest.raises(DeserializationError):
+            adapter.load_dict(data=payload)