diff --git a/autogen/agentchat/conversable_agent.py b/autogen/agentchat/conversable_agent.py
index 609a72b4768..0c6d4c8128e 100644
--- a/autogen/agentchat/conversable_agent.py
+++ b/autogen/agentchat/conversable_agent.py
@@ -130,6 +130,12 @@ def __init__(
             description (str): a short description of the agent. This description is used by other agents
                 (e.g. the GroupChatManager) to decide when to call upon this agent. (Default: system_message)
         """
+        # we change code_execution_config below and we have to make sure we don't change the input
+        # in case of UserProxyAgent, without this we could even change the default value {}
+        code_execution_config = (
+            code_execution_config.copy() if hasattr(code_execution_config, "copy") else code_execution_config
+        )
+
         self._name = name
         # a dictionary of conversations, default value is list
         self._oai_messages = defaultdict(list)
diff --git a/autogen/agentchat/user_proxy_agent.py b/autogen/agentchat/user_proxy_agent.py
index a92d58cfde1..980ca12c633 100644
--- a/autogen/agentchat/user_proxy_agent.py
+++ b/autogen/agentchat/user_proxy_agent.py
@@ -30,7 +30,7 @@ def __init__(
         max_consecutive_auto_reply: Optional[int] = None,
         human_input_mode: Literal["ALWAYS", "TERMINATE", "NEVER"] = "ALWAYS",
         function_map: Optional[Dict[str, Callable]] = None,
-        code_execution_config: Optional[Union[Dict, Literal[False]]] = None,
+        code_execution_config: Union[Dict, Literal[False]] = {},
         default_auto_reply: Optional[Union[str, Dict, None]] = "",
         llm_config: Optional[Union[Dict, Literal[False]]] = False,
         system_message: Optional[Union[str, List]] = "",
diff --git a/test/agentchat/test_agent_setup_with_use_docker_settings.py b/test/agentchat/test_agent_setup_with_use_docker_settings.py
index 8cda4466e16..4ec05ae1a75 100644
--- a/test/agentchat/test_agent_setup_with_use_docker_settings.py
+++ b/test/agentchat/test_agent_setup_with_use_docker_settings.py
@@ -16,17 +16,6 @@
     skip = False or skip_openai
 
 
-def get_current_autogen_env_var():
-    return os.environ.get("AUTOGEN_USE_DOCKER", None)
-
-
-def restore_autogen_env_var(current_env_value):
-    if current_env_value is None:
-        del os.environ["AUTOGEN_USE_DOCKER"]
-    else:
-        os.environ["AUTOGEN_USE_DOCKER"] = current_env_value
-
-
 def docker_running():
     return is_docker_running() or in_docker_container()
 
@@ -54,10 +43,9 @@ def test_agent_setup_with_use_docker_false():
 
 
 @pytest.mark.skipif(skip, reason="openai not installed")
-def test_agent_setup_with_env_variable_false_and_docker_running():
-    current_env_value = get_current_autogen_env_var()
+def test_agent_setup_with_env_variable_false_and_docker_running(monkeypatch):
+    monkeypatch.setenv("AUTOGEN_USE_DOCKER", "False")
 
-    os.environ["AUTOGEN_USE_DOCKER"] = "False"
     user_proxy = UserProxyAgent(
         name="test_agent",
         human_input_mode="NEVER",
@@ -65,21 +53,26 @@ def test_agent_setup_with_env_variable_false_and_docker_running():
 
     assert user_proxy._code_execution_config["use_docker"] is False
 
-    restore_autogen_env_var(current_env_value)
-
 
 @pytest.mark.skipif(skip or (not docker_running()), reason="openai not installed OR docker not running")
-def test_agent_setup_with_default_and_docker_running():
+def test_agent_setup_with_default_and_docker_running(monkeypatch):
+    monkeypatch.delenv("AUTOGEN_USE_DOCKER", raising=False)
+
+    assert os.getenv("AUTOGEN_USE_DOCKER") is None
+
     user_proxy = UserProxyAgent(
         name="test_agent",
         human_input_mode="NEVER",
     )
 
+    assert os.getenv("AUTOGEN_USE_DOCKER") is None
+
     assert user_proxy._code_execution_config["use_docker"] is True
 
 
 @pytest.mark.skipif(skip or (docker_running()), reason="openai not installed OR docker running")
-def test_raises_error_agent_setup_with_default_and_docker_not_running():
+def test_raises_error_agent_setup_with_default_and_docker_not_running(monkeypatch):
+    monkeypatch.delenv("AUTOGEN_USE_DOCKER", raising=False)
     with pytest.raises(RuntimeError):
         UserProxyAgent(
             name="test_agent",
@@ -88,10 +81,8 @@ def test_raises_error_agent_setup_with_default_and_docker_not_running():
 
 
 @pytest.mark.skipif(skip or (docker_running()), reason="openai not installed OR docker running")
-def test_raises_error_agent_setup_with_env_variable_true_and_docker_not_running():
-    current_env_value = get_current_autogen_env_var()
-
-    os.environ["AUTOGEN_USE_DOCKER"] = "True"
+def test_raises_error_agent_setup_with_env_variable_true_and_docker_not_running(monkeypatch):
+    monkeypatch.setenv("AUTOGEN_USE_DOCKER", "True")
 
     with pytest.raises(RuntimeError):
         UserProxyAgent(
@@ -99,14 +90,10 @@ def test_raises_error_agent_setup_with_env_variable_true_and_docker_not_running(
             human_input_mode="NEVER",
         )
 
-    restore_autogen_env_var(current_env_value)
-
 
 @pytest.mark.skipif(skip or (not docker_running()), reason="openai not installed OR docker not running")
-def test_agent_setup_with_env_variable_true_and_docker_running():
-    current_env_value = get_current_autogen_env_var()
-
-    os.environ["AUTOGEN_USE_DOCKER"] = "True"
+def test_agent_setup_with_env_variable_true_and_docker_running(monkeypatch):
+    monkeypatch.setenv("AUTOGEN_USE_DOCKER", "True")
 
     user_proxy = UserProxyAgent(
         name="test_agent",
@@ -114,5 +101,3 @@ def test_agent_setup_with_env_variable_true_and_docker_running():
     )
 
     assert user_proxy._code_execution_config["use_docker"] is True
-
-    restore_autogen_env_var(current_env_value)