diff --git a/lsh/__init__.py b/lsh/__init__.py
index 7403f25..cc7a2f7 100644
--- a/lsh/__init__.py
+++ b/lsh/__init__.py
@@ -135,7 +135,7 @@ def prepare_dup_buckets(cls, buckets, id=None):
 
     # public methods
 
-    def get_dup_buckets(self, doc):
+    def get_dup_buckets(self, doc, id):
         """
         Returns a list of buckets (which are themselves lists) that contain the ids
         of any matching documents.  If the cache was built in chronological order