diff --git a/mingw-w64-firefox/0020-gmp-clearkey-include-atomic-header.patch b/mingw-w64-firefox/0020-gmp-clearkey-include-atomic-header.patch
new file mode 100644
index 0000000000..7bf9466502
--- /dev/null
+++ b/mingw-w64-firefox/0020-gmp-clearkey-include-atomic-header.patch
@@ -0,0 +1,11 @@
+--- firefox-41.0b6/media/gmp-clearkey/0.1/VideoDecoder.h.orig	2015-09-01 01:26:48.000000000 +0100
++++ firefox-41.0b6/media/gmp-clearkey/0.1/VideoDecoder.h	2015-09-03 17:49:05.009038800 +0100
+@@ -24,6 +24,8 @@
+ 
+ #include "mfobjects.h"
+ 
++#include <atomic>
++
+ class VideoDecoder : public GMPVideoDecoder
+                    , public RefCounted
+ {
diff --git a/mingw-w64-firefox/PKGBUILD b/mingw-w64-firefox/PKGBUILD
index 619a0f889a..596f5a97b0 100644
--- a/mingw-w64-firefox/PKGBUILD
+++ b/mingw-w64-firefox/PKGBUILD
@@ -76,7 +76,7 @@ path_conv_for_make() {
 
 _realname=firefox
 pkgname=("${MINGW_PACKAGE_PREFIX}-${_realname}")
-pkgver=41.0b5
+pkgver=41.0b6
 pkgrel=1
 pkgdesc='Mozilla Firefox (mingw-w64)'
 groups=("${MINGW_PACKAGE_PREFIX}")
@@ -109,13 +109,14 @@ source=("http://ftp.mozilla.org/pub/mozilla.org/${_realname}/releases/${pkgver}/
         "0017-MSYS2-Dont-use--static-or--static-libgcc.patch"
         "0018-MSYS2-Allow-make-install.patch"
         "0019-Bug-id-1163452-MSYS2-Dont-MOZ_ASSERT-when-stdout-is-same-as-stderr.patch"
+        "0020-gmp-clearkey-include-atomic-header.patch"
         "debugging.patch"
         "mozconfig.x86_64"
         "mozconfig.i686"
         "config.sub"
         "config.guess")
 noextract=("${_realname}-${pkgver}.source.tar.xz")
-sha1sums=('f53aad21adfd6a2c9c013168b5195099b9e59536'
+sha1sums=('6b4c0d3a9a228b43d9682d57f74a1132f92dd329'
           '6c018e4ac903180f5f65492241502842dc1c035a'
           'c4e841bf724a1ff907592c8a11ba9683568acfd5'
           '1c0810fbfd6f336eec81e236c89c6c9ca0e79290'
@@ -136,7 +137,8 @@ sha1sums=('f53aad21adfd6a2c9c013168b5195099b9e59536'
           'bacec1492cb54096f7483b192918050e7cb1de1d'
           '9eead9e427a8158df42a2ec81bf7c9f38ad1c915'
           'e939e9722fd0cb70a7bd5e705b37bd47045e9647'
-          '018097900afc127e1142bd50d96c8d4df73ab13b'
+          '20a6613a688c2e7cb95a6faae49974e452dba8de'
+          '7f23896aeca52cd7bd3a038c5b5fd4eb68c90923'
           'c2a0ed20a82d212bb4aa84cb2f294be3ba0bb859'
           '02befff9986a31bbc4ad74a8c0125e84f29fcb40'
           '9f4a4161fd23ba603c3e8140b322e732a46efffc'
@@ -188,6 +190,7 @@ prepare() {
   patch -p1 -i "${srcdir}"/0017-MSYS2-Dont-use--static-or--static-libgcc.patch
   patch -p1 -i "${srcdir}"/0018-MSYS2-Allow-make-install.patch
   patch -p1 -i "${srcdir}"/0019-Bug-id-1163452-MSYS2-Dont-MOZ_ASSERT-when-stdout-is-same-as-stderr.patch
+  patch -p1 -i "${srcdir}"/0020-gmp-clearkey-include-atomic-header.patch
   # patch -p1 -i "${srcdir}"/debugging.patch
 
   find . -name config.sub -exec cp "${srcdir}"/config.sub {} \;