diff --git a/synapse/push/emailpusher.py b/synapse/push/emailpusher.py
index 2eb325c7c..c7afd1111 100644
--- a/synapse/push/emailpusher.py
+++ b/synapse/push/emailpusher.py
@@ -218,7 +218,8 @@ class EmailPusher(object):
         )
 
     def seconds_until(self, ts_msec):
-        return (ts_msec - self.clock.time_msec()) / 1000
+        secs = (ts_msec - self.clock.time_msec()) / 1000
+        return max(secs, 0)
 
     def get_room_throttle_ms(self, room_id):
         if room_id in self.throttle_params: