diff --git a/chapter06/meson.xml b/chapter06/meson.xml
index db3d67afc..5a8779a91 100644
--- a/chapter06/meson.xml
+++ b/chapter06/meson.xml
@@ -42,7 +42,7 @@
 
     <para>Apply a fix from upstream to fix a regression:</para>
 
-<screen><userinput remap="pre">sed -i "s@isfile(f)@&amp; and not f.startswith('/dev')@" mesonbuild/interpreter.py</userinput></screen>
+<screen><userinput remap="pre">sed -i "s@isfile(a)@&amp; and not a.startswith('/dev')@" mesonbuild/interpreter.py</userinput></screen>
 
     <para>Compile Meson with the following command:</para>