diff --git a/plone/scale/storage.py b/plone/scale/storage.py
index 725378b..ea18cbb 100644
--- a/plone/scale/storage.py
+++ b/plone/scale/storage.py
@@ -62,6 +62,7 @@ def scale(self, factory=None, **parameters):
         info = storage.get(key)
         modified = self.modified and self.modified()
         if info is not None and modified > info['modified']:
+            del storage[info['uid']]
             info = None     # invalidate when the image was updated
         if info is None and factory:
             result = factory(**parameters)
diff --git a/plone/scale/tests/test_storage.py b/plone/scale/tests/test_storage.py
index 21725c8..ece76cd 100644
--- a/plone/scale/tests/test_storage.py
+++ b/plone/scale/tests/test_storage.py
@@ -105,6 +105,18 @@ def testDeleteRemovesItemAndIndex(self):
         del storage[scale['uid']]
         self.assertEqual(len(storage), 0)
 
+    def testCleanUpOldItems(self):
+        storage = self.storage
+        scale_old = storage.scale(factory=self.factory, foo=23, bar=42)
+        next_modified = storage.modified() + 1
+        storage.modified = lambda: next_modified
+        scale_new = storage.scale(factory=self.factory, foo=23, bar=42)
+        self.assertEqual(len(storage), 2)
+        self.assertEqual(scale_new['uid'] in storage, True)
+        self.assertEqual(scale_old['uid'] in storage, False)
+        del storage[scale_new['uid']]
+        self.assertEqual(len(storage), 0)
+
 
 def test_suite():
     from unittest import defaultTestLoader