diff --git a/src/marvin/openai/ChatCompletion/__init__.py b/src/marvin/openai/ChatCompletion/__init__.py
index 38bbb3d22..339eef0b2 100644
--- a/src/marvin/openai/ChatCompletion/__init__.py
+++ b/src/marvin/openai/ChatCompletion/__init__.py
@@ -7,9 +7,10 @@
 import warnings
 
 from typing import Type, Optional, Union, Literal
+from pydantic import Extra
 
 
-class ChatCompletionConfig(BaseSettings):
+class ChatCompletionConfig(BaseSettings, extra=Extra.allow):
     model: str = "gpt-3.5-turbo"
     temperature: float = 0
     functions: list = Field(default_factory=list)
@@ -30,7 +31,7 @@ def merge(self, *args, **kwargs):
                 setattr(self, key, getattr(self, key, []) + value)
             else:
                 setattr(self, key, value)
-        return {k: v for k, v in self.__dict__.items() if v != []}
+        return {k: v for k, v in self.__dict__.items() if v}
 
 
 def process_list(lst):
@@ -68,18 +69,19 @@ def create(cls, *args, response_model: Optional[Type[BaseModel]] = None, **kwarg
                 }
         payload = config.merge(**kwargs)
         response = cls.observer(super(ChatCompletion, cls).create)(*args, **payload)
-        response.to_model = lambda: (
-            process_list(
-                list(
-                    map(
-                        lambda x: response_model.parse_raw(
-                            x.message.function_call.arguments
-                        ),
-                        response.choices,
+        if response_model is not None:
+            response.to_model = lambda: (
+                process_list(
+                    list(
+                        map(
+                            lambda x: response_model.parse_raw(
+                                x.message.function_call.arguments
+                            ),
+                            response.choices,
+                        )
                     )
                 )
             )
-        )
         return response
 
     @classmethod
@@ -105,18 +107,19 @@ async def acreate(
         response = await cls.observer(super(ChatCompletion, cls).acreate)(
             *args, **payload
         )
-        response.to_model = lambda: (
-            process_list(
-                list(
-                    map(
-                        lambda x: response_model.parse_raw(
-                            x.message.function_call.arguments
-                        ),
-                        response.choices,
+        if response_model is not None:
+            response.to_model = lambda: (
+                process_list(
+                    list(
+                        map(
+                            lambda x: response_model.parse_raw(
+                                x.message.function_call.arguments
+                            ),
+                            response.choices,
+                        )
                     )
                 )
             )
-        )
         return response
 
     @staticmethod