diff --git a/protocol/wayland.xml b/protocol/wayland.xml
index b9aa9f19..26e0d5c2 100644
--- a/protocol/wayland.xml
+++ b/protocol/wayland.xml
@@ -45,6 +45,8 @@
 	The object returned by this request will be destroyed by the
 	compositor after the callback is fired and as such the client must not
 	attempt to use it after that point.
+
+	The data passed in the callback is the event serial.
       </description>
       <arg name="callback" type="new_id" interface="wl_callback"/>
     </request>
@@ -170,7 +172,7 @@
       <description summary="done event">
        Notify the client when the related request is done.
       </description>
-      <arg name="serial" type="uint" summary="serial of the event"/>
+      <arg name="data" type="uint" summary="request-specific data for the wl_callback"/>
     </event>
   </interface>
 
@@ -1076,6 +1078,8 @@
 	The object returned by this request will be destroyed by the
 	compositor after the callback is fired and as such the client must not
 	attempt to use it after that point.
+
+	The data passed in the callback is the current time, in milliseconds.
       </description>
 
       <arg name="callback" type="new_id" interface="wl_callback"/>