diff --git a/en_US.ISO8859-1/books/porters-handbook/book.sgml b/en_US.ISO8859-1/books/porters-handbook/book.sgml
index ff89e5383c..3885ef49b8 100644
--- a/en_US.ISO8859-1/books/porters-handbook/book.sgml
+++ b/en_US.ISO8859-1/books/porters-handbook/book.sgml
@@ -1604,7 +1604,7 @@ RESOLUTION?=   300
       <programlisting>RESOLUTION=     118
 MASTERDIR=      ${.CURDIR}/../xdvi300
 
-.include ${MASTERDIR}/Makefile</programlisting>
+.include "${MASTERDIR}/Makefile"</programlisting>
 
       <para>(<filename>xdvi240/Makefile</filename> and
         <filename>xdvi400/Makefile</filename> are similar).  The