diff --git a/homeassistant/components/device_tracker/bluetooth_tracker.py b/homeassistant/components/device_tracker/bluetooth_tracker.py
index 807f6c0d0a4..2ca519d225c 100644
--- a/homeassistant/components/device_tracker/bluetooth_tracker.py
+++ b/homeassistant/components/device_tracker/bluetooth_tracker.py
@@ -40,7 +40,7 @@ def setup_scanner(hass, config, see, discovery_info=None):
         attributes = {}
         if rssi is not None:
             attributes['rssi'] = rssi
-        see(mac="{}_{}".format(BT_PREFIX, mac), host_name=name,
+        see(mac="{}{}".format(BT_PREFIX, mac), host_name=name,
             attributes=attributes, source_type=SOURCE_TYPE_BLUETOOTH)
 
     def discover_devices():