diff --git a/en_US.ISO8859-1/books/porters-handbook/book.sgml b/en_US.ISO8859-1/books/porters-handbook/book.sgml
index 2c5e2d82f8..f9cd232951 100644
--- a/en_US.ISO8859-1/books/porters-handbook/book.sgml
+++ b/en_US.ISO8859-1/books/porters-handbook/book.sgml
@@ -10047,6 +10047,17 @@ bacula:*:910:</programlisting>
 	      <makevar>NOT_FOR_ARCHS_REASON_<replaceable>ARCH</replaceable></makevar>.
 	  </listitem>
 
+	  <listitem>
+	    <para>If a port fetches i386 binaries and installs them,
+	      <makevar>IA32_BINARY_PORT</makevar> should be set.  If this
+	      variable is set, it will be checked whether the
+	      <filename>/usr/lib32</filename> directory is available for
+	      IA32 versions of libraries and whether the kernel
+	      has IA32 compatibility compiled in.  If one of these two
+	      dependencies is not satisfied, <makevar>IGNORE</makevar> will
+	      be set automatically.</para>
+	  </listitem>
+
 	</itemizedlist>
 
 	</sect2>