diff --git a/oml/cache.py b/oml/cache.py
index a56d299..28d521c 100644
--- a/oml/cache.py
+++ b/oml/cache.py
@@ -10,8 +10,8 @@ class Cache(dict):
         now = time.time()
         for k, value in list(self._added.items()):
             if value < now:
-                del self._added[k]
-                del self[k]
+                self._added.pop(k, None)
+                self.pop(k, None)
         return dict.get(self, key)
 
     def set(self, key, value, ttl=None):