diff --git a/docs/rules.md b/docs/rules.md
index 410c7043e7..014399209e 100644
--- a/docs/rules.md
+++ b/docs/rules.md
@@ -116,8 +116,9 @@ or the window's Window manager class or instance name starts with their string a
 
 `Device` conditions are true if a particular device originated the notification.
 `Active` conditions are true if a particular device is active.
-`Device` and `Active` conditions take one argument, which is the Serial number or Unit ID of a device,
+`Device` and `Active` conditions take one argument, which is the serial number or unit ID of a device,
 as shown in Solaar's detail pane.
+Some older devices do not have a useful serial number or unit ID and so cannot be tested for by these conditions.
 
 `Host' conditions are true if the computers hostname starts with the condition's argument.
 
diff --git a/lib/logitech_receiver/diversion.py b/lib/logitech_receiver/diversion.py
index cb6f27b25e..b0e5b2ead7 100644
--- a/lib/logitech_receiver/diversion.py
+++ b/lib/logitech_receiver/diversion.py
@@ -1051,8 +1051,7 @@ def __str__(self):
     def evaluate(self, feature, notification, device, status, last_result):
         if _log.isEnabledFor(_DEBUG):
             _log.debug('evaluate condition: %s', self)
-        dev = _Device.find(self.devID)
-        return device == dev
+        return device.unitId == self.devID or device.serial == self.devID
 
     def data(self):
         return {'Device': self.devID}