diff --git a/fastchat/serve/api_provider.py b/fastchat/serve/api_provider.py
index 2e967e3ef..dc15c82a6 100644
--- a/fastchat/serve/api_provider.py
+++ b/fastchat/serve/api_provider.py
@@ -348,6 +348,8 @@ def openai_api_stream_iter(
                 max_tokens=max_new_tokens,
                 stream=False,
             )
+        if not res.choices or res.choices[0].message is None:
+            return
         text = res.choices[0].message.content
         pos = 0
         while pos < len(text):
diff --git a/fastchat/serve/monitor/classify/label.py b/fastchat/serve/monitor/classify/label.py
index fe928a9ba..925167f81 100644
--- a/fastchat/serve/monitor/classify/label.py
+++ b/fastchat/serve/monitor/classify/label.py
@@ -64,6 +64,8 @@ def chat_completion_openai(model, messages, temperature, max_tokens, api_dict=No
                 max_tokens=max_tokens,
                 # extra_body={"guided_choice": GUIDED_CHOICES} if GUIDED_CHOICES else None,
             )
+            if not completion.choices or completion.choices[0].message is None:
+                break
             output = completion.choices[0].message.content
             # print(output)
             break
@@ -114,6 +116,8 @@ def chat_completion_anthropic(model, messages, temperature, max_tokens, api_dict
                 temperature=temperature,
                 system=sys_msg,
             )
+            if not response.content:
+                break
             output = response.content[0].text
             break
         except anthropic.APIError as e:
diff --git a/fastchat/serve/monitor/criteria_labeling.py b/fastchat/serve/monitor/criteria_labeling.py
index b08b030d4..75010a563 100644
--- a/fastchat/serve/monitor/criteria_labeling.py
+++ b/fastchat/serve/monitor/criteria_labeling.py
@@ -89,6 +89,8 @@ def chat_completion_openai(model, messages, temperature, max_tokens, api_dict=No
                 max_tokens=max_tokens,
                 # extra_body={"guided_choice": GUIDED_CHOICES} if GUIDED_CHOICES else None,
             )
+            if not completion.choices or completion.choices[0].message is None:
+                break
             output = completion.choices[0].message.content
             break
         except openai.RateLimitError as e: