diff --git a/homeassistant/components/discovery.py b/homeassistant/components/discovery.py
index 96c79053dff..bbf40c73070 100644
--- a/homeassistant/components/discovery.py
+++ b/homeassistant/components/discovery.py
@@ -134,6 +134,7 @@ async def async_setup(hass, config):
 
         discovery_hash = json.dumps([service, info], sort_keys=True)
         if discovery_hash in already_discovered:
+            logger.debug("Already discoverd service %s %s.", service, info)
             return
 
         already_discovered.add(discovery_hash)