diff --git a/nonebot/config.py b/nonebot/config.py
index b714d1d9..89bdc55a 100644
--- a/nonebot/config.py
+++ b/nonebot/config.py
@@ -17,6 +17,7 @@ from ipaddress import IPv4Address
 from typing import TYPE_CHECKING, Any, Set, Dict, Tuple, Union, Mapping, Optional
 
 from pydantic.utils import deep_update
+from pydantic.fields import Undefined, UndefinedType
 from pydantic import Extra, Field, BaseSettings, IPvAnyAddress
 from pydantic.env_settings import (
     DotenvType,
@@ -44,19 +45,22 @@ class CustomEnvSettings(EnvSettingsSource):
         env_vars = {**env_file_vars, **env_vars}
 
         for field in settings.__fields__.values():
-            env_val: Optional[str] = None
+            env_val: Union[str, None, UndefinedType] = Undefined
             for env_name in field.field_info.extra["env_names"]:
-                env_val = env_vars.get(env_name)
+                env_val = env_vars.get(env_name, Undefined)
                 if env_name in env_file_vars:
                     del env_file_vars[env_name]
-                if env_val is not None:
+                if env_val is not Undefined:
                     break
 
             is_complex, allow_parse_failure = self.field_is_complex(field)
             if is_complex:
-                if env_val is None:
+                if isinstance(env_val, UndefinedType):
+                    # field is complex but no value found so far, try explode_env_vars
                     if env_val_built := self.explode_env_vars(field, env_vars):
                         d[field.alias] = env_val_built
+                elif env_val is None:
+                    d[field.alias] = env_val
                 else:
                     # field is complex and there's a value
                     # decode that as JSON, then add explode_env_vars
@@ -74,7 +78,7 @@ class CustomEnvSettings(EnvSettingsSource):
                         )
                     else:
                         d[field.alias] = env_val
-            elif env_val is not None:
+            elif not isinstance(env_val, UndefinedType):
                 # simplest case, field is not complex
                 # we only need to add the value if it was found
                 d[field.alias] = env_val
diff --git a/tests/.env.test b/tests/.env.test
index e4fba171..6479747a 100644
--- a/tests/.env.test
+++ b/tests/.env.test
@@ -1,6 +1,8 @@
 LOG_LEVEL=TRACE
 NICKNAME=["test"]
 SUPERUSERS=["test", "fake:faketest"]
+API_TIMEOUT
+SIMPLE_NONE
 COMMON_OVERRIDE=new
 CONFIG_FROM_ENV=
 CONFIG_OVERRIDE=old
diff --git a/tests/test_init.py b/tests/test_init.py
index 9040c2d0..016082fb 100644
--- a/tests/test_init.py
+++ b/tests/test_init.py
@@ -20,6 +20,11 @@ async def test_init():
     assert env == "test"
 
     config = nonebot.get_driver().config
+    assert config.nickname == {"test"}
+    assert config.superusers == {"test", "fake:faketest"}
+    assert config.api_timeout is None
+
+    assert config.simple_none is None
     assert config.config_from_env == {"test": "test"}
     assert config.config_override == "new"
     assert config.config_from_init == "init"