diff --git a/udev/udev.xml b/udev/udev.xml
index 6085dfff24..682cc3f959 100644
--- a/udev/udev.xml
+++ b/udev/udev.xml
@@ -466,7 +466,8 @@
           <term><option>WAIT_FOR</option></term>
           <listitem>
             <para>Wait for a file to become available or until a 10
-            seconds timeout expires.</para>
+            seconds timeout expires. The path is relative to the sysfs device,
+            i. e. if no path is specified this waits for an attribute to appear.</para>
           </listitem>
         </varlistentry>