diff --git a/brozzler/frontier.py b/brozzler/frontier.py
index 3608d06..c9e0e9b 100644
--- a/brozzler/frontier.py
+++ b/brozzler/frontier.py
@@ -27,7 +27,7 @@ class RethinkDbFrontier:
         if not "sites" in tables:
             self.logger.info("creating rethinkdb table 'sites' in database %s", repr(self.r.dbname))
             self.r.table_create("sites", shards=self.shards, replicas=self.replicas).run()
-            self.r.table("sites").index_create("sites_last_disclaimed", [self.r.row["status"], self.r.row["claimed"], self.r.row["last_disclaimed"]]).run()
+            self.r.table("sites").index_create("sites_last_disclaimed", [self.r.row["status"], self.r.row["last_disclaimed"]]).run()
             self.r.table("sites").index_create("job_id").run()
         if not "pages" in tables:
             self.logger.info("creating rethinkdb table 'pages' in database %s", repr(self.r.dbname))
@@ -93,14 +93,24 @@ class RethinkDbFrontier:
         while True:
             result = (self.r.table("sites")
                     .between(
-                        ["ACTIVE",False,rethinkdb.minval],
-                        ["ACTIVE",False,rethinkdb.maxval],
+                        ["ACTIVE",rethinkdb.minval],
+                        ["ACTIVE",rethinkdb.maxval],
                         index="sites_last_disclaimed")
                     .order_by(index="sites_last_disclaimed").limit(1)
+                    .filter(
+                        (rethinkdb.row["claimed"] != True) |
+                        (rethinkdb.row["last_disclaimed"]
+                            < rethinkdb.now() - 2*60*60))
                     .update({"claimed":True,"last_claimed_by":worker_id},
                         return_changes=True)).run()
             self._vet_result(result, replaced=[0,1], unchanged=[0,1])
             if result["replaced"] == 1:
+                if result["changes"][0]["old_val"]["claimed"]:
+                    self.logger.warn(
+                            "re-claimed site that was still marked 'claimed' "
+                            "because it was last disclaimed a long time ago "
+                            "at %s",
+                            result["changes"][0]["old_val"]["last_disclaimed"])
                 site = brozzler.Site(**result["changes"][0]["new_val"])
             else:
                 raise brozzler.NothingToClaim