diff --git a/videv.py b/videv.py
index c9006af..076b3a2 100644
--- a/videv.py
+++ b/videv.py
@@ -169,13 +169,15 @@ class all_off(videv_base):
             mqtt_client.add_callback(all_off_topic, self.all_off)
 
     def __check_inst_capabilities__(self, name, inst):
-        # fits to specified classes
-        try:
-            # all_off method is callable
-            return callable(inst.all_off)
-        except AttributeError:
-            # all_off method does not exist
-            return False
+        if hasattr(inst, "ADD_TO_VIDEV_ALL_OFF"):
+            # fits to specified classes
+            try:
+                # all_off method is callable
+                return callable(inst.all_off)
+            except AttributeError:
+                # all_off method does not exist
+                return False
+        return False
 
     def __add_instances__(self, name, inst, level=0):
         if self.__check_inst_capabilities__(name, inst):