diff --git a/ChangeLog b/ChangeLog
index a9f4c51f..7d92425e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -3,6 +3,7 @@
 	* man/useradd.8.xml: Document the /etc/default/useradd variables.
 	* man/useradd.8.xml: Fix the documentation of the GROUP variable
 	(and -g/--gid option).
+	* man/useradd.8.xml: Document that -o is only valid with -u
 
 2008-08-29  Nicolas François  <nicolas.francois@centraliens.net>
 
diff --git a/TODO b/TODO
index 098d463b..0dcb5211 100644
--- a/TODO
+++ b/TODO
@@ -23,10 +23,6 @@ WITH_SELINUX
 chage, chfn, chsh: same change needed as in passwd.
   - probably need moving check_selinux_access to a separate file.
 
-useradd manpage
-  - add -k option
-  - mention that -o require -u
-
 testsuite
  - newgrp
    - test with unknown user's GID
diff --git a/man/useradd.8.xml b/man/useradd.8.xml
index 81253fc8..7d502efb 100644
--- a/man/useradd.8.xml
+++ b/man/useradd.8.xml
@@ -318,6 +318,10 @@
 	</term>
 	<listitem>
 	  <para>Allow the creation of a user account with a duplicate (non-unique) UID.</para>
+	  <para>
+	    This option is only valid in combination with the
+	    <option>-o</option> option.
+	  </para>
 	</listitem>
       </varlistentry>
       <varlistentry>