diff --git a/protocol/wayland.xml b/protocol/wayland.xml
index 61e0366d..9955d247 100644
--- a/protocol/wayland.xml
+++ b/protocol/wayland.xml
@@ -1905,6 +1905,10 @@
 	wl_surface is no longer used as the cursor. When the use as a
 	cursor ends, the current and pending input regions become
 	undefined, and the wl_surface is unmapped.
+
+	The serial parameter must match the latest wl_pointer.enter
+	serial number sent to the client. Otherwise the request will be
+	ignored.
       </description>
       <arg name="serial" type="uint" summary="serial number of the enter event"/>
       <arg name="surface" type="object" interface="wl_surface" allow-null="true"