diff --git a/pkgs/development/tools/parsing/flex/flex-2.5.35.nix b/pkgs/development/tools/parsing/flex/default.nix
similarity index 100%
rename from pkgs/development/tools/parsing/flex/flex-2.5.35.nix
rename to pkgs/development/tools/parsing/flex/default.nix
diff --git a/pkgs/development/tools/parsing/flex/flex-2.5.33.nix b/pkgs/development/tools/parsing/flex/flex-2.5.33.nix
deleted file mode 100644
index 9be98689aea..00000000000
--- a/pkgs/development/tools/parsing/flex/flex-2.5.33.nix
+++ /dev/null
@@ -1,20 +0,0 @@
-# !!! this should be moved to default.nix eventually (but I delay
-# doing that since it would cause a rebuild of lots of stuff).
-
-{stdenv, fetchurl, yacc, m4}:
-
-assert yacc != null && m4 != null;
-
-stdenv.mkDerivation {
-  name = "flex-2.5.33";
-  src = fetchurl {
-    url = mirror://sourceforge/flex/flex-2.5.33.tar.bz2;
-    md5 = "343374a00b38d9e39d1158b71af37150";
-  };
-  buildInputs = [yacc];
-  propagatedBuildInputs = [m4];
-
-  meta = {
-    description = "A fast lexical analyser generator";
-  };
-}
diff --git a/pkgs/development/tools/parsing/flex/flex-2.5.34.nix b/pkgs/development/tools/parsing/flex/flex-2.5.34.nix
deleted file mode 100644
index d56cf0c88a2..00000000000
--- a/pkgs/development/tools/parsing/flex/flex-2.5.34.nix
+++ /dev/null
@@ -1,19 +0,0 @@
-# This should be moved to default.nix eventually (?)
-
-{stdenv, fetchurl, yacc, m4}:
-
-assert yacc != null && m4 != null;
-
-stdenv.mkDerivation {
-  name = "flex-2.5.34";
-  src = fetchurl {
-    url = mirror://sourceforge/flex/flex-2.5.34.tar.bz2;
-    sha256 = "1c8e64f32508841b0441ddfb139c4cfd25fee3728cadb63f5f351c6eb9b224a6";
-  };
-  buildInputs = [yacc];
-  propagatedBuildInputs = [m4];
-
-  meta = {
-    description = "A fast lexical analyser generator";
-  };
-}
diff --git a/pkgs/development/tools/parsing/flex/flex-2.5.4a.nix b/pkgs/development/tools/parsing/flex/flex-2.5.4a.nix
deleted file mode 100644
index 13bb6834979..00000000000
--- a/pkgs/development/tools/parsing/flex/flex-2.5.4a.nix
+++ /dev/null
@@ -1,12 +0,0 @@
-{stdenv, fetchurl, yacc}:
-
-assert yacc != null;
-
-stdenv.mkDerivation {
-  name = "flex-2.5.4a";
-  src = fetchurl {
-    url = mirror://sourceforge/flex/flex-2.5.4a.tar.gz;
-    md5 = "bd8753d0b22e1f4ec87a553a73021adf";
-  };
-  buildInputs = [yacc];
-}
diff --git a/pkgs/top-level/all-packages.nix b/pkgs/top-level/all-packages.nix
index 3cde58bd2ad..c7e371e7fd7 100644
--- a/pkgs/top-level/all-packages.nix
+++ b/pkgs/top-level/all-packages.nix
@@ -3550,29 +3550,12 @@ let
 
   checkstyle = callPackage ../development/tools/analysis/checkstyle { };
 
-  flex = flex2535;
-
-  flex2535 = callPackage ../development/tools/parsing/flex/flex-2.5.35.nix {
+  flex = callPackage ../development/tools/parsing/flex {
     # Break infinite recursion: bison's test suite needs flex, so we
     # use an untested bison build to build flex first.
     yacc = bison.override { flex = null; };
   };
 
-  flex2534 = callPackage ../development/tools/parsing/flex/flex-2.5.34.nix {
-    yacc = bison.override { flex = null; };
-  };
-
-  flex2533 = callPackage ../development/tools/parsing/flex/flex-2.5.33.nix {
-    yacc = bison.override { flex = null; };
-  };
-
-  # Note: 2.5.4a is much older than 2.5.35 but happens first when sorting
-  # alphabetically, hence the low priority.
-  flex254a = lowPrio (import ../development/tools/parsing/flex/flex-2.5.4a.nix {
-    inherit fetchurl stdenv;
-    yacc = bison.override { flex = null; };
-  });
-
   m4 = gnum4;
 
   global = callPackage ../development/tools/misc/global { };
diff --git a/pkgs/top-level/release-small.nix b/pkgs/top-level/release-small.nix
index 28d503d85fe..caf1bd60665 100644
--- a/pkgs/top-level/release-small.nix
+++ b/pkgs/top-level/release-small.nix
@@ -46,7 +46,6 @@ with import ./release-lib.nix { inherit supportedSystems; };
   file = all;
   findutils = all;
   flex = all;
-  flex2535 = all;
   gcc = all;
   gcc33 = linux;
   gcc34 = linux;
diff --git a/pkgs/top-level/release.nix b/pkgs/top-level/release.nix
index 1aae2ce4ee2..a9a45b9d57a 100644
--- a/pkgs/top-level/release.nix
+++ b/pkgs/top-level/release.nix
@@ -106,7 +106,6 @@ let
       file = all;
       findutils = all;
       flex = all;
-      flex2535 = all;
       fontforge = linux;
       fuse = linux;
       gajim = linux;