diff --git a/CHANGES.rst b/CHANGES.rst
index 1bfdc7c..5ab00d6 100644
--- a/CHANGES.rst
+++ b/CHANGES.rst
@@ -4,6 +4,12 @@ Changelog
 Here you can see the full list of changes between each SQLAlchemy-Utils release.
 
 
+0.12.3 (2013-05-30)
+^^^^^^^^^^^^^^^^^^^
+
+- Proxy dict expiration listener from function scope to global scope
+
+
 0.12.2 (2013-05-29)
 ^^^^^^^^^^^^^^^^^^^
 
diff --git a/setup.py b/setup.py
index bd47d7c..f6735ec 100644
--- a/setup.py
+++ b/setup.py
@@ -24,7 +24,7 @@ class PyTest(Command):
 
 setup(
     name='SQLAlchemy-Utils',
-    version='0.12.2',
+    version='0.12.3',
     url='https://github.com/kvesteri/sqlalchemy-utils',
     license='BSD',
     author='Konsta Vesterinen',
diff --git a/sqlalchemy_utils/proxy_dict.py b/sqlalchemy_utils/proxy_dict.py
index 17d79d2..6b33fef 100644
--- a/sqlalchemy_utils/proxy_dict.py
+++ b/sqlalchemy_utils/proxy_dict.py
@@ -59,10 +59,6 @@ def proxy_dict(parent, collection_name, mapping_attr):
     try:
         parent._proxy_dicts
     except AttributeError:
-        def expire_proxy_dicts(target, context):
-            target._proxy_dicts = {}
-
-        sa.event.listen(parent.__class__, 'expire', expire_proxy_dicts)
         parent._proxy_dicts = {}
 
     try:
@@ -74,3 +70,11 @@ def proxy_dict(parent, collection_name, mapping_attr):
             mapping_attr
         )
     return parent._proxy_dicts[collection_name]
+
+
+def expire_proxy_dicts(target, context):
+    if hasattr(target, '_proxy_dicts'):
+        target._proxy_dicts = {}
+
+
+sa.event.listen(sa.orm.mapper, 'expire', expire_proxy_dicts)