diff --git a/man/udevadm.xml b/man/udevadm.xml
index d12c39b765..c2f2bc95d2 100644
--- a/man/udevadm.xml
+++ b/man/udevadm.xml
@@ -528,8 +528,11 @@
           <term><option>-a</option></term>
           <term><option>--action=<replaceable>ACTION</replaceable></option></term>
           <listitem>
-            <para>The action string. The special value <literal>help</literal> may be used to list
-            known values.</para>
+            <para>Type of event to be simulated. Possible actions are <literal>add</literal>,
+            <literal>remove</literal>, <literal>change</literal>, <literal>move</literal>,
+            <literal>online</literal>, <literal>offline</literal>, <literal>bind</literal>,
+            and <literal>unbind</literal>. Also, the special value <literal>help</literal> can be used
+            to list the possible actions. The default value is <literal>add</literal>.</para>
           </listitem>
         </varlistentry>
         <varlistentry>