diff --git a/lib/network.py b/lib/network.py
index a3fce97f3..66d009feb 100644
--- a/lib/network.py
+++ b/lib/network.py
@@ -835,7 +835,6 @@ class Network(util.DaemonThread):
             if b:
                 interface.mode = 'default'
                 interface.blockchain = b
-                #interface.print_error('passed checkpoint', b.filename)
                 self.queue_request('blockchain.headers.subscribe', [], interface)
             else:
                 interface.print_error("checkpoint failed")
@@ -850,12 +849,13 @@ class Network(util.DaemonThread):
                 interface.print_error("binary search")
                 next_height = (interface.bad + interface.good) // 2
             else:
-                interface.bad = height
-                delta = interface.tip - height
-                next_height = interface.tip - 2 * delta
-                if next_height < 0:
-                    interface.print_error("header didn't connect, dismissing interface")
+                if height == 0:
                     self.connection_down(interface.server)
+                    next_height = None
+                else:
+                    interface.bad = height
+                    delta = interface.tip - height
+                    next_height = max(0, interface.tip - 2 * delta)
         elif interface.mode == 'binary':
             if can_connect:
                 interface.good = height