diff --git a/protocol/wayland.xml b/protocol/wayland.xml
index 5a6a189d..c4737529 100644
--- a/protocol/wayland.xml
+++ b/protocol/wayland.xml
@@ -304,7 +304,8 @@
 
 	The drm format codes match the macros defined in drm_fourcc.h, except
 	argb8888 and xrgb8888. The formats actually supported by the compositor
-	will be reported by the format event.
+	will be reported by the format event. See drm_fourcc.h for more detailed
+	format descriptions.
 
 	For all wl_shm formats and unless specified in another protocol
 	extension, pre-multiplied alpha is used for pixel values.
@@ -474,6 +475,10 @@
 	Informs the client about a valid pixel format that
 	can be used for buffers. Known formats include
 	argb8888 and xrgb8888.
+
+	Extensions to drm_fourcc.h (or the format enum) do not require
+	increasing the wl_shm version; as a result, clients may receive format
+	codes which were not in the list at the time the client was made.
       </description>
       <arg name="format" type="uint" enum="format" summary="buffer pixel format"/>
     </event>