diff --git a/chapter04/flex.xml b/chapter04/flex.xml
index 04c543bce..e8e4c14fd 100644
--- a/chapter04/flex.xml
+++ b/chapter04/flex.xml
@@ -1,2 +1,2 @@
 Flex (&flex-version;) - &flex-size;:
-<ulink url="http://freshmeat.net/projects/flex/"/>
+<ulink url="ftp://ftp.gnu.org/pub/non-gnu/flex/"/>
diff --git a/entities/flex.ent b/entities/flex.ent
index 0bb0364c7..577619c97 100644
--- a/entities/flex.ent
+++ b/entities/flex.ent
@@ -9,7 +9,7 @@
 <!ENTITY aa-flex-down SYSTEM "../appendixa/flex-down.xml">
 <!ENTITY aa-flex-shortdesc SYSTEM "../appendixa/flex-shortdesc.xml">
 
-<!ENTITY flex-version "2.5.31">
+<!ENTITY flex-version "2.5.4a">
 <!ENTITY flex-depversion "2.5.4a">
 <!ENTITY flex-contversion "2.5.4a">
 <!ENTITY flex-size "372 KB">