diff --git a/components/xl9535.rst b/components/xl9535.rst
index 6eeae6010..e67a52d31 100644
--- a/components/xl9535.rst
+++ b/components/xl9535.rst
@@ -50,7 +50,7 @@ Pin configuration variables:
 ****************************
 
 - **xl9535** (**Required**, :ref:`config-id`): The id of the ``xl9535`` component of the pin.
-- **number** (**Required**, int): The pin number.
+- **number** (**Required**, int): The pin number. Valid numbers are 0-7 and 10-17.
 - **inverted** (*Optional*, boolean): If all read and written values
   should be treated as inverted. Defaults to ``false``.
 - **mode** (*Optional*, string): A pin mode to set for the pin at. One of ``INPUT`` or ``OUTPUT``.