diff --git a/hassio/api/addons.py b/hassio/api/addons.py
index bfdc03780..5509713eb 100644
--- a/hassio/api/addons.py
+++ b/hassio/api/addons.py
@@ -54,8 +54,8 @@ class APIAddons(object):
         """Return a simplified device list."""
         dev_list = addon.devices
         if not dev_list:
-            return []
-        return [row.split(':')[0] for row in dev_list]
+            return
+        return set(row.split(':')[0] for row in dev_list)
 
     @api_process
     async def list(self, request):