diff --git a/docs/commandref.html b/docs/commandref.html
index cbc9a0f34..5658d7aec 100644
--- a/docs/commandref.html
+++ b/docs/commandref.html
@@ -2286,7 +2286,9 @@ A line ending with \ will be concatenated with the next one, so long lines
   The state contains the fill level in % (lower case v in the device state)
   and the current volume in liters (upper case V in the device state).
   Measured distance to the liquid's surface, fill level, volume and warnings
-  (Test mode, Battery low) are available.<br>
+  (Test mode, Battery low) are available. Due to the design of the USF1000S
+  protocol, you can have only one USF1000S in range of your FHZ as these
+  devices cannot be distinguished.<br>
   <br>
 
   <a name="USF1000Define"></a>