diff --git a/pkgs/applications/networking/browsers/firefox/default.nix b/pkgs/applications/networking/browsers/firefox/default.nix
index 27363482be0..9869e24ce5a 100644
--- a/pkgs/applications/networking/browsers/firefox/default.nix
+++ b/pkgs/applications/networking/browsers/firefox/default.nix
@@ -17,9 +17,9 @@ assert stdenv.gcc ? libc && stdenv.gcc.libc != null;
 
 rec {
 
-  firefoxVersion = "26.0";
+  firefoxVersion = "27.0";
 
-  xulVersion = "26.0"; # this attribute is used by other packages
+  xulVersion = "27.0"; # this attribute is used by other packages
 
 
   src = fetchurl {
@@ -29,7 +29,7 @@ rec {
         # Fall back to this url for versions not available at releases.mozilla.org.
         "http://ftp.mozilla.org/pub/mozilla.org/firefox/releases/${firefoxVersion}/source/firefox-${firefoxVersion}.source.tar.bz2"
     ];
-    sha1 = "f7c6642d6f62aea8d4eced48dd27aba0634edcd5";
+    sha1 = "ec2031385237e30be829817ac79caa8e80cc2a14";
   };
 
   commonConfigureFlags =
@@ -162,13 +162,20 @@ rec {
       "SYSTEM_LIBXUL=1"
     ];
 
-    # Hack to work around make's idea of -lbz2 dependency
+    # Because preConfigure runs configure from a subdirectory.
+    configureScript = "../configure";
+
     preConfigure =
       ''
+        # Hack to work around make's idea of -lbz2 dependency
         find . -name Makefile.in -execdir sed -i '{}' -e '1ivpath %.so ${
           stdenv.lib.concatStringsSep ":"
             (map (s : s + "/lib") (buildInputs ++ [stdenv.gcc.libc]))
         }' ';'
+
+        # Building directly in the main source directory is not allowed.
+        mkdir obj_dir
+        cd obj_dir
       '';
 
     postInstall =
diff --git a/pkgs/applications/video/gnash/default.nix b/pkgs/applications/video/gnash/default.nix
index 0291e7593ea..c3b78b64d93 100644
--- a/pkgs/applications/video/gnash/default.nix
+++ b/pkgs/applications/video/gnash/default.nix
@@ -81,6 +81,8 @@ stdenv.mkDerivation rec {
        echo "\$GST_PLUGIN_PATH set to \`$GST_PLUGIN_PATH'"
     '';
 
+  postConfigure = "echo '#define nullptr NULL' >> gnashconfig.h";
+
   # Make sure `gtk-gnash' gets `libXext' in its `RPATH'.
   NIX_LDFLAGS="-lX11 -lXext";
 
diff --git a/pkgs/development/libraries/nss/default.nix b/pkgs/development/libraries/nss/default.nix
index b352064cee5..92cc12fe1be 100644
--- a/pkgs/development/libraries/nss/default.nix
+++ b/pkgs/development/libraries/nss/default.nix
@@ -5,17 +5,17 @@
 let
 
   nssPEM = fetchurl {
-    url = http://dev.gentoo.org/~anarchy/patches/nss-3.15-pem-support-20130617.patch.xz;
-    sha256 = "1k1m8lsgqwxx251943hks1dd13hz1adpqqb0hxwn011by5vmi201";
+    url = http://dev.gentoo.org/~polynomial-c/mozilla/nss-3.15.4-pem-support-20140109.patch.xz;
+    sha256 = "10ibz6y0hknac15zr6dw4gv9nb5r5z9ym6gq18j3xqx7v7n3vpdw";
   };
 
 in stdenv.mkDerivation rec {
   name = "nss-${version}";
-  version = "3.15.3.1";
+  version = "3.15.4";
 
   src = fetchurl {
-    url = "http://ftp.mozilla.org/pub/mozilla.org/security/nss/releases/NSS_3_15_3_1_RTM/src/${name}.tar.gz";
-    sha1 = "4e0f81a1f770447dc5440201a579151b601463e2";
+    url = "http://ftp.mozilla.org/pub/mozilla.org/security/nss/releases/NSS_3_15_4_RTM/src/${name}.tar.gz";
+    sha1 = "c164fac83fcbaff010786767e2a858ca23a89a5b";
   };
 
   buildInputs = [ nspr perl zlib sqlite ];