diff --git a/slic/core/device/filtered.py b/slic/core/device/filtered.py
index 2fae0912..4e8d30e4 100644
--- a/slic/core/device/filtered.py
+++ b/slic/core/device/filtered.py
@@ -3,17 +3,20 @@ from .simpledevice import SimpleDevice
 
 
 def by_type(dev, typ):
-    #TODO: adjust ID, name, description
-    res = SimpleDevice(dev.ID, name=dev.name, description=dev.description)
+    res = {}
     for k, v in dev.__dict__.items():
         if isinstance(v, typ):
-            new = v
+            res[k] = v
         elif isinstance(v, Device):
             new = by_type(v, typ)
-        else:
-            continue # ignore not matching
-        res.__dict__[k] = new
-    return res
+            if new:
+                res[k] = new
+
+    if res:
+        #TODO: adjust ID, name, description
+        return SimpleDevice(dev.ID, name=dev.name, description=dev.description, **res)
+    else:
+        return None