diff --git a/chapter05/gcc-pass1.xml b/chapter05/gcc-pass1.xml
index affb97a1d..b47e822dc 100644
--- a/chapter05/gcc-pass1.xml
+++ b/chapter05/gcc-pass1.xml
@@ -122,7 +122,9 @@ fi</userinput></screen>
     --disable-libvtv          \
     --disable-libstdcxx       \
     --enable-languages=c,c++  \
-    $NAN_SWITCH</userinput></screen>
+    $NAN_SWITCH
+
+unset NAN_SWITCH</userinput></screen>
     <variablelist>
       <title>The meaning of the configure options:</title>