diff --git a/en_US.ISO8859-1/books/porters-handbook/book.sgml b/en_US.ISO8859-1/books/porters-handbook/book.sgml
index 0a64da150a..3b539f9bf3 100644
--- a/en_US.ISO8859-1/books/porters-handbook/book.sgml
+++ b/en_US.ISO8859-1/books/porters-handbook/book.sgml
@@ -5576,7 +5576,9 @@ PLIST_SUB=      OCTAVE_VERSION=${OCTAVE_VERSION}</programlisting>
 		  <row>
 		    <entry>5.1-CURRENT after 16550 UART constants moved from
 		      <filename>&lt;dev/sio/sioreg.h&gt;</filename> to
-		      <filename>&lt;dev/ic/ns16550.h&gt;</filename>.</entry>
+		      <filename>&lt;dev/ic/ns16550.h&gt;</filename>.
+		      Also when libmap functionality was unconditional
+		      supported by rtld.</entry>
 		    <entry>501107</entry>
 		  </row>
 		  <row>