diff --git a/burr/integrations/persisters/b_asyncpg.py b/burr/integrations/persisters/b_asyncpg.py
index c694350d5..c47e34e39 100644
--- a/burr/integrations/persisters/b_asyncpg.py
+++ b/burr/integrations/persisters/b_asyncpg.py
@@ -370,7 +370,7 @@ async def load(
 
     async def save(
         self,
-        partition_key: str,
+        partition_key: Optional[str],
         app_id: str,
         sequence_id: int,
         position: str,
@@ -395,6 +395,8 @@ async def save(
             before the action was applied.
         :return: None
         """
+        if partition_key is None:
+            partition_key = self.PARTITION_KEY_DEFAULT
         logger.debug(
             "saving %s, %s, %s, %s, %s, %s",
             partition_key,
diff --git a/burr/integrations/persisters/b_psycopg2.py b/burr/integrations/persisters/b_psycopg2.py
index 26425f805..7c0430a7f 100644
--- a/burr/integrations/persisters/b_psycopg2.py
+++ b/burr/integrations/persisters/b_psycopg2.py
@@ -216,7 +216,7 @@ def load(
 
     def save(
         self,
-        partition_key: str,
+        partition_key: Optional[str],
         app_id: str,
         sequence_id: int,
         position: str,
@@ -241,6 +241,8 @@ def save(
             before the action was applied.
         :return: None
         """
+        if partition_key is None:
+            partition_key = self.PARTITION_KEY_DEFAULT
         logger.debug(
             "saving %s, %s, %s, %s, %s, %s",
             partition_key,
diff --git a/tests/integrations/persisters/test_postgresql.py b/tests/integrations/persisters/test_postgresql.py
index 0e8cd700a..0100cd93e 100644
--- a/tests/integrations/persisters/test_postgresql.py
+++ b/tests/integrations/persisters/test_postgresql.py
@@ -49,6 +49,13 @@ def test_save_and_load_state(postgresql_persister):
     assert data["state"].get_all() == {"a": 1, "b": 2}
 
 
+def test_save_and_load_with_default_partition_key(postgresql_persister):
+    """An application without a partition key saves and loads with partition_key=None."""
+    postgresql_persister.save(None, "no_pk_app", 1, "pos", state.State({"a": 1}), "completed")
+    data = postgresql_persister.load(None, "no_pk_app")
+    assert data["state"].get_all() == {"a": 1}
+
+
 def test_list_app_ids(postgresql_persister):
     postgresql_persister.save("pk", "app_id1", 1, "pos1", state.State({"a": 1}), "completed")
     postgresql_persister.save("pk", "app_id2", 2, "pos2", state.State({"b": 2}), "completed")
@@ -146,6 +153,15 @@ async def test_async_save_and_load_state(asyncpostgresql_persister):
     assert data["state"].get_all() == {"a": 1, "b": 2}
 
 
+async def test_async_save_and_load_with_default_partition_key(asyncpostgresql_persister):
+    """An application without a partition key saves and loads with partition_key=None."""
+    await asyncpostgresql_persister.save(
+        None, "no_pk_app", 1, "pos", state.State({"a": 1}), "completed"
+    )
+    data = await asyncpostgresql_persister.load(None, "no_pk_app")
+    assert data["state"].get_all() == {"a": 1}
+
+
 async def test_async_list_app_ids(asyncpostgresql_persister):
     await asyncpostgresql_persister.save(
         "pk", "app_id1", 1, "pos1", state.State({"a": 1}), "completed"