diff --git a/nonebot/plugin/__init__.py b/nonebot/plugin/__init__.py
index 425590d4..f4457d5c 100644
--- a/nonebot/plugin/__init__.py
+++ b/nonebot/plugin/__init__.py
@@ -7,7 +7,6 @@
 import re
 import json
 from types import ModuleType
-from functools import reduce
 from dataclasses import dataclass
 from collections import defaultdict
 from contextvars import Context, copy_context
diff --git a/nonebot/plugin/manager.py b/nonebot/plugin/manager.py
index 2cb97d79..b317da97 100644
--- a/nonebot/plugin/manager.py
+++ b/nonebot/plugin/manager.py
@@ -89,8 +89,20 @@ class PluginManager:
         if hasattr(_internal_space, internal_id):
             raise RuntimeError("Plugin manager already exists!")
 
-        prefix = sys._getframe(3).f_globals.get(
-            "__name__") or _internal_space.__name__
+        index = 2
+        prefix: str = _internal_space.__name__
+        while True:
+            try:
+                frame = sys._getframe(index)
+            except ValueError:
+                break
+            # check if is called in plugin
+            if "__plugin_name__" not in frame.f_globals:
+                index += 1
+                continue
+            prefix = frame.f_globals.get("__name__", _internal_space.__name__)
+            break
+
         if not prefix.startswith(_internal_space.__name__):
             prefix = _internal_space.__name__
         module = _InternalModule(prefix, self)