diff --git a/docs/Reference.md b/docs/Reference.md
index 51e6742..0c85f02 100644
--- a/docs/Reference.md
+++ b/docs/Reference.md
@@ -217,6 +217,14 @@ The following methods are supported:
   * returns a pointer to the Characteristic itself so that the method can be chained during instantiation
   * example: `(new Characteristic::Brightness(50))->setRange(10,100,5);`
   
+* `SpanCharacteristic *setValidValues(int n, [int v1, int v2 ...])`
+  * overrides the default HAP Valid Values for Characteristics that have specific enumerated Valid Values with a variable-length list of *n* values *v1*, *v2*, etc.
+  * an error is thrown if:
+    * called on a Characteristic that does not have specific enumerated Valid Values, or
+    * called more than once on the same Characteristic
+  * returns a pointer to the Characteristic itself so that the method can be chained during instantiation
+  * example: `(new Characteristic::SecuritySystemTargetState())->setValidValues(3,0,1,3);` creates a new valid value list of length=3 containing the values 0, 1, and 3.  This has the effect of informing the HomeKit that a SecuritySystemTargetState value of 2 (Night Arm) is not valid and should not be shown as a choice in the Home App
+
 ## *SpanButton(int pin, uint16_t longTime, uint16_t singleTime, uint16_t doubleTime)*
 
 Creating an instance of this **class** attaches a pushbutton handler to the ESP32 *pin* specified.