diff --git a/ChangeLog b/ChangeLog
index db1872fa..c670c50e 100644
--- a/ChangeLog
+++ b/ChangeLog
@@ -1,3 +1,9 @@
+2013-08-13  Nicolas François  <nicolas.francois@centraliens.net>
+
+	* man/login.defs.d/SUB_GID_COUNT.xml: Document that the behavior
+	of useradd and newusers depends on the existence of /etc/subgid.
+	* man/login.defs.d/SUB_UID_COUNT.xml: Likewise for /etc/subuid.
+
 2013-08-13  Nicolas François  <nicolas.francois@centraliens.net>
 
 	* src/useradd.c: Change message in case of find_new_sub_uids /
diff --git a/man/login.defs.d/SUB_GID_COUNT.xml b/man/login.defs.d/SUB_GID_COUNT.xml
index e3ef8064..d8592e64 100644
--- a/man/login.defs.d/SUB_GID_COUNT.xml
+++ b/man/login.defs.d/SUB_GID_COUNT.xml
@@ -32,8 +32,9 @@
   <term><option>SUB_GID_COUNT</option> (number)</term>
   <listitem>
     <para>
-      The commands <command>useradd</command> and <command>newusers</command>
-      allocate <option>SUB_GID_COUNT</option> unused group IDs from the range
+      If <filename>/etc/subuid</filename> exists, the commands
+      <command>useradd</command> and <command>newusers</command> allocate
+      <option>SUB_GID_COUNT</option> unused group IDs from the range
       <option>SUB_GID_MIN</option> to <option>SUB_GID_MAX</option> for each
       new user.
     </para>
diff --git a/man/login.defs.d/SUB_UID_COUNT.xml b/man/login.defs.d/SUB_UID_COUNT.xml
index 5afd3473..8db10690 100644
--- a/man/login.defs.d/SUB_UID_COUNT.xml
+++ b/man/login.defs.d/SUB_UID_COUNT.xml
@@ -32,8 +32,9 @@
   <term><option>SUB_UID_COUNT</option> (number)</term>
   <listitem>
     <para>
-      The commands <command>useradd</command> and <command>newusers</command>
-      allocate <option>SUB_UID_COUNT</option> unused user IDs from the range
+      If <filename>/etc/subuid</filename> exists, the commands
+      <command>useradd</command> and <command>newusers</command> allocate
+      <option>SUB_UID_COUNT</option> unused user IDs from the range
       <option>SUB_UID_MIN</option> to <option>SUB_UID_MAX</option> for each
       new user.
     </para>