diff --git a/wpa_supplicant/doc/docbook/wpa_supplicant.sgml b/wpa_supplicant/doc/docbook/wpa_supplicant.sgml
index 02012d1b0..9a7d60119 100644
--- a/wpa_supplicant/doc/docbook/wpa_supplicant.sgml
+++ b/wpa_supplicant/doc/docbook/wpa_supplicant.sgml
@@ -2,7 +2,7 @@
 
 <refentry>
   <refentryinfo>
-    <date>07 August 2019</date>
+    <date>13 September 2022</date>
   </refentryinfo>
 
   <refmeta>
@@ -22,6 +22,7 @@
       <arg>-D<replaceable>driver</replaceable></arg>
       <arg>-P<replaceable>PID_file</replaceable></arg>
       <arg>-f<replaceable>output file</replaceable></arg>
+      <arg>-I<replaceable>additional config file</replaceable></arg>
     </cmdsynopsis>
   </refsynopsisdiv>
   <refsect1>
@@ -340,6 +341,13 @@
 	</listitem>
       </varlistentry>
 
+      <varlistentry>
+	<term>-I filename</term>
+	<listitem>
+          <para>Path to additional configuration file.</para>
+	</listitem>
+      </varlistentry>
+
       <varlistentry>
 	<term>-d</term>
 	<listitem>