diff --git a/CHANGELOG.md b/CHANGELOG.md
index 0751fd6..41fbf38 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -11,6 +11,10 @@ All notable changes to this project will be documented in this file.
 - Type-hint-driven validation via `df_loads(s, expected_type=...)`: when the V2 programming model provides a return-type annotation for an activity or sub-orchestrator, the annotation is threaded through call sites so the SDK's `df_loads` can validate the deserialized payload against that type (when available). On older `azure-functions` releases the argument is accepted but ignored.
 - Return-type discovery for V2 decorated activities/sub-orchestrators (`azure.durable_functions.models.utils.type_discovery`): resolves the concrete return annotation from the user's registered function, used to supply `expected_type` to `df_loads`.
 
+### Changed
+
+- `purge_instance_history_by` now raises a clear `ValueError` when the required `created_time_from` argument is omitted, instead of sending a request that the Durable extension rejects.
+
 ## 1.0.0b6
 
 - [Create timer](https://github.com/Azure/azure-functions-durable-python/issues/35) functionality available
diff --git a/azure/durable_functions/models/DurableOrchestrationClient.py b/azure/durable_functions/models/DurableOrchestrationClient.py
index 3f587e2..c3d32c6 100644
--- a/azure/durable_functions/models/DurableOrchestrationClient.py
+++ b/azure/durable_functions/models/DurableOrchestrationClient.py
@@ -423,7 +423,8 @@ async def purge_instance_history_by(
         Parameters
         ----------
         created_time_from : Optional[datetime]
-            Delete orchestration history which were created after this Date.
+            Delete orchestration history which were created after this Date. This argument
+            is required.
         created_time_to: Optional[datetime]
             Delete orchestration history which were created before this Date.
         runtime_status: Optional[List[OrchestrationRuntimeStatus]]
@@ -434,7 +435,15 @@ async def purge_instance_history_by(
         -------
         PurgeHistoryResult
             The results of the request to purge history
+
+        Raises
+        ------
+        ValueError
+            When `created_time_from` is not provided.
         """
+        if created_time_from is None:
+            raise ValueError("created_time_from is required when purging instance history")
+
         options = RpcManagementOptions(created_time_from=created_time_from,
                                        created_time_to=created_time_to,
                                        runtime_status=runtime_status)
diff --git a/tests/models/test_DurableOrchestrationClient.py b/tests/models/test_DurableOrchestrationClient.py
index 38a1059..27df446 100644
--- a/tests/models/test_DurableOrchestrationClient.py
+++ b/tests/models/test_DurableOrchestrationClient.py
@@ -1,4 +1,5 @@
 import json
+from datetime import datetime
 from typing import Any
 
 import pytest
@@ -366,40 +367,61 @@ async def test_delete_500_purge_instance_history(binding_string):
 
 @pytest.mark.asyncio
 async def test_delete_200_purge_instance_history_by(binding_string):
-    mock_request = MockRequest(expected_url=f"{RPC_BASE_URL}instances/?runtimeStatus=Running",
-                               response=[200, dict(instancesDeleted=1)])
+    mock_request = MockRequest(
+        expected_url=f"{RPC_BASE_URL}instances/"
+                     "?createdTimeFrom=2000-01-01T00:00:00.000000Z"
+                     "&runtimeStatus=Completed",
+        response=[200, dict(instancesDeleted=1)])
     client = DurableOrchestrationClient(binding_string)
     client._delete_async_request = mock_request.delete
 
     result = await client.purge_instance_history_by(
-        runtime_status=[OrchestrationRuntimeStatus.Running])
+        created_time_from=datetime(2000, 1, 1),
+        runtime_status=[OrchestrationRuntimeStatus.Completed])
     assert result is not None
     assert result.instances_deleted == 1
 
 
 @pytest.mark.asyncio
 async def test_delete_404_purge_instance_history_by(binding_string):
-    mock_request = MockRequest(expected_url=f"{RPC_BASE_URL}instances/?runtimeStatus=Running",
-                               response=[404, MESSAGE_404])
+    mock_request = MockRequest(
+        expected_url=f"{RPC_BASE_URL}instances/"
+                     "?createdTimeFrom=2000-01-01T00:00:00.000000Z"
+                     "&runtimeStatus=Completed",
+        response=[404, MESSAGE_404])
     client = DurableOrchestrationClient(binding_string)
     client._delete_async_request = mock_request.delete
 
     result = await client.purge_instance_history_by(
-        runtime_status=[OrchestrationRuntimeStatus.Running])
+        created_time_from=datetime(2000, 1, 1),
+        runtime_status=[OrchestrationRuntimeStatus.Completed])
     assert result is not None
     assert result.instances_deleted == 0
 
 
 @pytest.mark.asyncio
 async def test_delete_500_purge_instance_history_by(binding_string):
-    mock_request = MockRequest(expected_url=f"{RPC_BASE_URL}instances/?runtimeStatus=Running",
-                               response=[500, MESSAGE_500])
+    mock_request = MockRequest(
+        expected_url=f"{RPC_BASE_URL}instances/"
+                     "?createdTimeFrom=2000-01-01T00:00:00.000000Z"
+                     "&runtimeStatus=Completed",
+        response=[500, MESSAGE_500])
     client = DurableOrchestrationClient(binding_string)
     client._delete_async_request = mock_request.delete
 
     with pytest.raises(Exception):
         await client.purge_instance_history_by(
-            runtime_status=[OrchestrationRuntimeStatus.Running])
+            created_time_from=datetime(2000, 1, 1),
+            runtime_status=[OrchestrationRuntimeStatus.Completed])
+
+
+@pytest.mark.asyncio
+async def test_purge_instance_history_by_requires_created_time_from(binding_string):
+    client = DurableOrchestrationClient(binding_string)
+
+    with pytest.raises(ValueError, match="created_time_from is required"):
+        await client.purge_instance_history_by(
+            runtime_status=[OrchestrationRuntimeStatus.Completed])
 
 
 @pytest.mark.asyncio