diff --git a/pkgs/development/tools/parsing/bison/default.nix b/pkgs/development/tools/parsing/bison/default.nix
index da5873595cf..c699d815eb6 100644
--- a/pkgs/development/tools/parsing/bison/default.nix
+++ b/pkgs/development/tools/parsing/bison/default.nix
@@ -1,11 +1,11 @@
 { stdenv, fetchurl, m4, perl }:
 
 stdenv.mkDerivation rec {
-  name = "bison-2.6.4";
+  name = "bison-2.6.5";
 
   src = fetchurl {
     url = "mirror://gnu/bison/${name}.tar.xz";
-    sha256 = "e0c3179ed1a622d7ab9679d64b556a7722f9eb7fa32d568ce8f329f89cca52e9";
+    sha256 = "8640d5b51aad462db6863711f333a9159836853e0b1e79fdef708c6efb5cd52b";
   };
 
   buildNativeInputs = [ m4 ] ++ stdenv.lib.optional doCheck perl;
diff --git a/pkgs/tools/misc/grub/2.0x.nix b/pkgs/tools/misc/grub/2.0x.nix
index d0e7738b68e..e85e8de3dd8 100644
--- a/pkgs/tools/misc/grub/2.0x.nix
+++ b/pkgs/tools/misc/grub/2.0x.nix
@@ -49,17 +49,10 @@ stdenv.mkDerivation rec {
        sed -i '/gets is a security hole/d' grub-core/gnulib/stdio.in.h
     '';
 
-  # Source code generated by bison 2.6.4 contains pragmas that trigger
-  # warnings when built with -Wunknown-pragmas. Since Grub compiles with
-  # -Werror, this causes the build to fail. We work around this issue by
-  # ignoring pragma-related warnings, but clearly it would be better if
-  # Bison wouldn't trigger that issue in the first place. A bug report
-  # has been sent.
   prePatch =
     '' gunzip < "${unifont_bdf}" > "unifont.bdf"
        sed -i "configure" \
-           -e "s|/usr/src/unifont.bdf|$PWD/unifont.bdf|g" \
-           -e "s|-Wunknown-pragmas|-Wno-pragmas|g"
+           -e "s|/usr/src/unifont.bdf|$PWD/unifont.bdf|g"
     '';
 
   configureFlags =