diff --git a/custom_components/spook/util.py b/custom_components/spook/util.py
index cf9871d2..66ee4eb0 100644
--- a/custom_components/spook/util.py
+++ b/custom_components/spook/util.py
@@ -176,7 +176,7 @@ def async_filter_known_device_ids(
     return {
         device_id
         for device_id in device_ids - known_device_ids
-        if isinstance(device_id, str)
+        if device_id and isinstance(device_id, str)
     }