diff --git a/pisi/search/invertedindex.py b/pisi/search/invertedindex.py
index ea42c952..4f8d4657 100644
--- a/pisi/search/invertedindex.py
+++ b/pisi/search/invertedindex.py
@@ -39,7 +39,10 @@ class InvertedIndex(object):
     def query(self, terms, txn = None):
         def proc(txn):
             docs = [ self.get_term(x, txn) for x in terms ]
-            return reduce(lambda x,y: x.intersection(y), docs)
+            if docs:
+                return reduce(lambda x,y: x.intersection(y), docs)
+            else:
+                return set()
         return self.d.txn_proc(proc, txn)
 
     def list_terms(self, txn= None):