diff --git a/.changeset/yellow-berries-play.md b/.changeset/yellow-berries-play.md
new file mode 100644
index 000000000..2f94493c3
--- /dev/null
+++ b/.changeset/yellow-berries-play.md
@@ -0,0 +1,5 @@
+---
+"livekit-plugins-openai": patch
+---
+
+skip processing of choice.delta when it is None
diff --git a/livekit-plugins/livekit-plugins-openai/livekit/plugins/openai/llm.py b/livekit-plugins/livekit-plugins-openai/livekit/plugins/openai/llm.py
index e531932db..8dcb67a65 100644
--- a/livekit-plugins/livekit-plugins-openai/livekit/plugins/openai/llm.py
+++ b/livekit-plugins/livekit-plugins-openai/livekit/plugins/openai/llm.py
@@ -349,6 +349,11 @@ async def __anext__(self):
     def _parse_choice(self, choice: Choice) -> llm.ChatChunk | None:
         delta = choice.delta
 
+        # https://github.com/livekit/agents/issues/688
+        # the delta can be None when using Azure OpenAI using content filtering
+        if delta is None:
+            return None
+
         if delta.tool_calls:
             # check if we have functions to calls
             for tool in delta.tool_calls: