diff --git a/homeassistant/components/slack/notify.py b/homeassistant/components/slack/notify.py
index 8fb45c36d9f..5fff857825b 100644
--- a/homeassistant/components/slack/notify.py
+++ b/homeassistant/components/slack/notify.py
@@ -32,7 +32,6 @@ ATTR_PASSWORD = "password"
 ATTR_PATH = "path"
 ATTR_URL = "url"
 ATTR_USERNAME = "username"
-ATTR_USERNAME = "username"
 
 CONF_DEFAULT_CHANNEL = "default_channel"