diff --git a/minode/shared.py b/minode/shared.py
index 72864ec..a964dca 100644
--- a/minode/shared.py
+++ b/minode/shared.py
@@ -63,4 +63,3 @@ outgoing_connections = 8
 connection_limit = 250
 
 objects = {}
-objects_lock = threading.Lock()
diff --git a/minode/sql.py b/minode/sql.py
index 755f194..f1b3cd3 100644
--- a/minode/sql.py
+++ b/minode/sql.py
@@ -2,6 +2,7 @@
 
 import os
 import sqlite3
+import threading
 import time
 
 from . import shared, structure
@@ -12,6 +13,7 @@ sqlite3.threadsafety = 3
 class Inventory():
     """sqlite inventory"""
     def __init__(self):
+        self._lock = threading.Lock()
         self._db = sqlite3.connect(
             os.path.join(shared.data_directory, 'objects.dat'),
             check_same_thread=False
@@ -52,7 +54,7 @@ class Inventory():
 
     def cleanup(self):
         """Remove expired objects"""
-        with shared.objects_lock:
+        with self._lock:
             self._db.execute(
                 'DELETE FROM objects WHERE expires < ?',
                 (int(time.time()) - 3 * 3600,)
@@ -121,13 +123,13 @@ class Inventory():
         return item
 
     def __delitem__(self, vector):
-        with shared.objects_lock:  # KeyError
+        with self._lock:  # KeyError
             self._db.execute('DELETE FROM objects WHERE vector = ?', (vector,))
             self._db.commit()
             self.rowid = len(self)
 
     def __setitem__(self, vector, obj):
-        with shared.objects_lock:
+        with self._lock:
             cur = self._db.execute(
                 'INSERT INTO objects VALUES (?,?,?,?,?,?,?,?)', (
                     vector, obj.expires_time, obj.object_type, obj.version,