diff --git a/litellm/tests/test_get_optional_params_functions_not_supported.py b/litellm/tests/test_get_optional_params_functions_not_supported.py
new file mode 100644
index 000000000..2abfbc41f
--- /dev/null
+++ b/litellm/tests/test_get_optional_params_functions_not_supported.py
@@ -0,0 +1,9 @@
+import litellm
+from litellm import get_optional_params
+
+litellm.add_function_to_prompt = True
+optional_params = get_optional_params(
+    tools= [{'type': 'function', 'function': {'description': 'Get the current weather in a given location', 'name': 'get_current_weather', 'parameters': {'type': 'object', 'properties': {'location': {'type': 'string', 'description': 'The city and state, e.g. San Francisco, CA'}, 'unit': {'type': 'string', 'enum': ['celsius', 'fahrenheit']}}, 'required': ['location']}}}],
+    tool_choice= 'auto',
+)
+assert optional_params is not None
\ No newline at end of file
diff --git a/litellm/utils.py b/litellm/utils.py
index 75d6f8b7f..c0241f1c3 100644
--- a/litellm/utils.py
+++ b/litellm/utils.py
@@ -5769,7 +5769,7 @@ def get_optional_params(
         optional_params["extra_body"] = extra_body
     else:
         # if user passed in non-default kwargs for specific providers/models, pass them along
-        for k in passed_params.keys():
+        for k in list(passed_params.keys()):
             if k not in default_params.keys():
                 optional_params[k] = passed_params[k]
     print_verbose(f"Final returned optional params: {optional_params}")