diff --git a/reference/mbstring/configure.xml b/reference/mbstring/configure.xml
index 524b358ea2..df03406eb2 100644
--- a/reference/mbstring/configure.xml
+++ b/reference/mbstring/configure.xml
@@ -33,6 +33,20 @@
       <option role="configure">--disable-mbregex</option>: Disable
       regular expression functions with multibyte character support.
      </para>
+     <para>
+      <productname>Oniguruma</productname> is necessary for the regular
+      expression functions with multibyte character support.
+      <productname>Oniguruma</productname> is bundled with
+      <literal>mbstring</literal>. As of PHP 5.4.0, if
+      <productname>Oniguruma</productname> is already installed on the system,
+      <option role="configure">--with-onig[=DIR]</option> can be specified to
+      use the installed library.
+     </para>
+     <para>
+      As of PHP 5.4.0 it is possible to disable the multibyte regex backtrack
+      check by specifying <option
+      role="configure">--disable-mbregex-backtrack</option>.
+     </para>
     </listitem>
    </itemizedlist>
   </para>