diff --git a/sdk/eventgrid/azure-eventgrid/CHANGELOG.md b/sdk/eventgrid/azure-eventgrid/CHANGELOG.md
index 2b91553c0709..2421976a45f9 100644
--- a/sdk/eventgrid/azure-eventgrid/CHANGELOG.md
+++ b/sdk/eventgrid/azure-eventgrid/CHANGELOG.md
@@ -1,6 +1,6 @@
 # Release History
 
-## 4.2.0 (2021-05-11)
+## 4.2.0 (2021-05-12)
 
   **New Features**
   - Added new event names to the `SystemEventNames` enum.
diff --git a/sdk/eventgrid/azure-eventgrid/azure/eventgrid/_event_mappings.py b/sdk/eventgrid/azure-eventgrid/azure/eventgrid/_event_mappings.py
index 1b2f518a52d1..da2593bacb96 100644
--- a/sdk/eventgrid/azure-eventgrid/azure/eventgrid/_event_mappings.py
+++ b/sdk/eventgrid/azure-eventgrid/azure/eventgrid/_event_mappings.py
@@ -12,6 +12,48 @@ class SystemEventNames(str, Enum):
     Azure Event Grid. To check the list of recognizable system topics,
     visit https://docs.microsoft.com/azure/event-grid/system-topics.
     """
+    # these names below are for backward compat only - refrain from using them.
+    AcsChatMemberAddedToThreadWithUserEventName = 'Microsoft.Communication.ChatMemberAddedToThreadWithUser'
+
+    ResourceWriteFailureEventName = 'Microsoft.Resources.ResourceWriteFailure'
+
+    IoTHubDeviceDeletedEventName = 'Microsoft.Devices.DeviceDeleted'
+
+    IoTHubDeviceDisconnectedEventName = 'Microsoft.Devices.DeviceDisconnected'
+
+    ResourceDeleteFailureEventName = 'Microsoft.Resources.ResourceDeleteFailure'
+
+    ResourceDeleteCancelEventName = 'Microsoft.Resources.ResourceDeleteCancel'
+
+    AcsChatThreadParticipantAddedEventName = 'Microsoft.Communication.ChatThreadParticipantAdded'
+
+    ResourceDeleteSuccessEventName = 'Microsoft.Resources.ResourceDeleteSuccess'
+
+    EventGridSubscriptionValidationEventName = 'Microsoft.EventGrid.SubscriptionValidationEvent'
+
+    ResourceWriteSuccessEventName = 'Microsoft.Resources.ResourceWriteSuccess'
+
+    ResourceActionSuccessEventName = 'Microsoft.Resources.ResourceActionSuccess'
+
+    ResourceWriteCancelEventName = 'Microsoft.Resources.ResourceWriteCancel'
+
+    ServiceBusDeadletterMessagesAvailableWithNoListenerEventName = 'Microsoft.ServiceBus.DeadletterMessagesAvailableWithNoListener'
+
+    ResourceActionFailureEventName = 'Microsoft.Resources.ResourceActionFailure'
+
+    AcsChatMemberRemovedFromThreadWithUserEventName = 'Microsoft.Communication.ChatMemberRemovedFromThreadWithUser'
+
+    IoTHubDeviceConnectedEventName = 'Microsoft.Devices.DeviceConnected'
+
+    EventGridSubscriptionDeletedEventName = 'Microsoft.EventGrid.SubscriptionDeletedEvent'
+
+    AcsChatThreadParticipantRemovedEventName = 'Microsoft.Communication.ChatThreadParticipantRemoved'
+
+    ResourceActionCancelEventName = 'Microsoft.Resources.ResourceActionCancel'
+
+    IoTHubDeviceCreatedEventName = 'Microsoft.Devices.DeviceCreated'
+
+    # backward compat names end here.
     AcsChatMessageDeletedEventName = 'Microsoft.Communication.ChatMessageDeleted'
 
     AcsChatMessageDeletedInThreadEventName = 'Microsoft.Communication.ChatMessageDeletedInThread'
@@ -98,7 +140,7 @@ class SystemEventNames(str, Enum):
 
     KeyVaultSecretNewVersionCreatedEventName = 'Microsoft.KeyVault.SecretNewVersionCreated'
 
-    MachineLearningServicesNamesetDriftDetectedEventName = 'Microsoft.MachineLearningServices.DatasetDriftDetected'
+    MachineLearningServicesDatasetDriftDetectedEventName = 'Microsoft.MachineLearningServices.DatasetDriftDetected'
 
     MachineLearningServicesModelDeployedEventName = 'Microsoft.MachineLearningServices.ModelDeployed'
 
@@ -150,7 +192,7 @@ class SystemEventNames(str, Enum):
 
     MediaLiveEventEncoderDisconnectedEventName = 'Microsoft.Media.LiveEventEncoderDisconnected'
 
-    MediaLiveEventIncomingNameChunkDroppedEventName = 'Microsoft.Media.LiveEventIncomingDataChunkDropped'
+    MediaLiveEventIncomingDataChunkDroppedEventName = 'Microsoft.Media.LiveEventIncomingDataChunkDropped'
 
     MediaLiveEventIncomingStreamReceivedEventName = 'Microsoft.Media.LiveEventIncomingStreamReceived'
 
@@ -253,44 +295,3 @@ class SystemEventNames(str, Enum):
     WebSlotSwapWithPreviewCancelledEventName = 'Microsoft.Web.SlotSwapWithPreviewCancelled'
 
     WebSlotSwapWithPreviewStartedEventName = 'Microsoft.Web.SlotSwapWithPreviewStarted'
-
-    # these names below are for backward compat only - refrain from using them.
-    AcsChatMemberAddedToThreadWithUserEventName = 'Microsoft.Communication.ChatMemberAddedToThreadWithUser'
-
-    ResourceWriteFailureEventName = 'Microsoft.Resources.ResourceWriteFailure'
-
-    IoTHubDeviceDeletedEventName = 'Microsoft.Devices.DeviceDeleted'
-
-    IoTHubDeviceDisconnectedEventName = 'Microsoft.Devices.DeviceDisconnected'
-
-    ResourceDeleteFailureEventName = 'Microsoft.Resources.ResourceDeleteFailure'
-
-    ResourceDeleteCancelEventName = 'Microsoft.Resources.ResourceDeleteCancel'
-
-    AcsChatThreadParticipantAddedEventName = 'Microsoft.Communication.ChatThreadParticipantAdded'
-
-    ResourceDeleteSuccessEventName = 'Microsoft.Resources.ResourceDeleteSuccess'
-
-    EventGridSubscriptionValidationEventName = 'Microsoft.EventGrid.SubscriptionValidationEvent'
-
-    ResourceWriteSuccessEventName = 'Microsoft.Resources.ResourceWriteSuccess'
-
-    ResourceActionSuccessEventName = 'Microsoft.Resources.ResourceActionSuccess'
-
-    ResourceWriteCancelEventName = 'Microsoft.Resources.ResourceWriteCancel'
-
-    ServiceBusDeadletterMessagesAvailableWithNoListenerEventName = 'Microsoft.ServiceBus.DeadletterMessagesAvailableWithNoListener'
-
-    ResourceActionFailureEventName = 'Microsoft.Resources.ResourceActionFailure'
-
-    AcsChatMemberRemovedFromThreadWithUserEventName = 'Microsoft.Communication.ChatMemberRemovedFromThreadWithUser'
-
-    IoTHubDeviceConnectedEventName = 'Microsoft.Devices.DeviceConnected'
-
-    EventGridSubscriptionDeletedEventName = 'Microsoft.EventGrid.SubscriptionDeletedEvent'
-
-    AcsChatThreadParticipantRemovedEventName = 'Microsoft.Communication.ChatThreadParticipantRemoved'
-
-    ResourceActionCancelEventName = 'Microsoft.Resources.ResourceActionCancel'
-
-    IoTHubDeviceCreatedEventName = 'Microsoft.Devices.DeviceCreated'
diff --git a/sdk/eventgrid/azure-eventgrid/swagger/postprocess_eventnames.py b/sdk/eventgrid/azure-eventgrid/swagger/postprocess_eventnames.py
index ad20925542ce..3e818204da80 100644
--- a/sdk/eventgrid/azure-eventgrid/swagger/postprocess_eventnames.py
+++ b/sdk/eventgrid/azure-eventgrid/swagger/postprocess_eventnames.py
@@ -42,12 +42,12 @@ def event_tuples(system_events):
     return tup_list
 
 def generate_enum_content(tuples):
-    for tup in tup_list:
-        print(tup[0] + " = '" + tup[1] + "'\n")
     print("# these names below are for backward compat only - refrain from using them.")
     for k, v in backward_compat.items():
         print(k + " = '" + v + "'\n")
-
+    print("# backward compat names end here.")
+    for tup in tup_list:
+        print(tup[0] + " = '" + tup[1] + "'\n")
 system_events = [m for m in inspect.getmembers(models) if m[0].endswith('Data')]
 tup_list = event_tuples(system_events)