diff --git a/pymongo/mongo_client.py b/pymongo/mongo_client.py
index cbafe39a95..d26a398f95 100644
--- a/pymongo/mongo_client.py
+++ b/pymongo/mongo_client.py
@@ -636,7 +636,7 @@ def _cache_index(self, dbname, collection, index, cache_for):
         expire = datetime.timedelta(seconds=cache_for) + now
 
         with self.__index_cache_lock:
-            if database not in self.__index_cache:
+            if dbname not in self.__index_cache:
                 self.__index_cache[dbname] = {}
                 self.__index_cache[dbname][collection] = {}
                 self.__index_cache[dbname][collection][index] = expire