diff --git a/b2g/config/mozconfigs/common b/b2g/config/mozconfigs/common
index fdf0f49f4a461..1dae99bacbed5 100644
--- a/b2g/config/mozconfigs/common
+++ b/b2g/config/mozconfigs/common
@@ -2,6 +2,6 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-# This file is included by all b2g mozconfigs
+# This file is included at the top of all b2g mozconfigs
 
 . "$topsrcdir/build/mozconfig.common"
diff --git a/b2g/config/mozconfigs/common.override b/b2g/config/mozconfigs/common.override
new file mode 100644
index 0000000000000..b94b773c00323
--- /dev/null
+++ b/b2g/config/mozconfigs/common.override
@@ -0,0 +1,7 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file is included at the bottom of all b2g mozconfigs
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/b2g/config/mozconfigs/gb_armv7a_gecko/debug b/b2g/config/mozconfigs/gb_armv7a_gecko/debug
index 5cdc7a4480825..dee1f6b84dedd 100644
--- a/b2g/config/mozconfigs/gb_armv7a_gecko/debug
+++ b/b2g/config/mozconfigs/gb_armv7a_gecko/debug
@@ -17,3 +17,5 @@ ENABLE_MARIONETTE=1
 
 # Enable dump() from JS.
 export CXXFLAGS=-DMOZ_ENABLE_JS_DUMP
+
+. "$topsrcdir/b2g/config/mozconfigs/common.override"
diff --git a/b2g/config/mozconfigs/gb_armv7a_gecko/nightly b/b2g/config/mozconfigs/gb_armv7a_gecko/nightly
index 4bdd3cb6b8ea1..e5fdbb3605103 100644
--- a/b2g/config/mozconfigs/gb_armv7a_gecko/nightly
+++ b/b2g/config/mozconfigs/gb_armv7a_gecko/nightly
@@ -17,3 +17,5 @@ ENABLE_MARIONETTE=1
 
 # Enable dump() from JS.
 export CXXFLAGS=-DMOZ_ENABLE_JS_DUMP
+
+. "$topsrcdir/b2g/config/mozconfigs/common.override"
diff --git a/b2g/config/mozconfigs/ics_armv7a_gecko/debug b/b2g/config/mozconfigs/ics_armv7a_gecko/debug
index 64e0fa88a3f21..675ec9050b233 100644
--- a/b2g/config/mozconfigs/ics_armv7a_gecko/debug
+++ b/b2g/config/mozconfigs/ics_armv7a_gecko/debug
@@ -18,3 +18,5 @@ ENABLE_MARIONETTE=1
 
 # Enable dump() from JS.
 export CXXFLAGS="-DMOZ_ENABLE_JS_DUMP -include $topsrcdir/gonk-toolchain/gonk-misc/Unicode.h -include $topsrcdir/gonk-toolchain/system/vold/ResponseCode.h"
+
+. "$topsrcdir/b2g/config/mozconfigs/common.override"
diff --git a/b2g/config/mozconfigs/ics_armv7a_gecko/nightly b/b2g/config/mozconfigs/ics_armv7a_gecko/nightly
index 94e355a890d42..2bbbd13a0c558 100644
--- a/b2g/config/mozconfigs/ics_armv7a_gecko/nightly
+++ b/b2g/config/mozconfigs/ics_armv7a_gecko/nightly
@@ -20,3 +20,5 @@ ENABLE_MARIONETTE=1
 
 # Enable dump() from JS.
 export CXXFLAGS="-DMOZ_ENABLE_JS_DUMP -include $topsrcdir/gonk-toolchain/gonk-misc/Unicode.h -include $topsrcdir/gonk-toolchain/system/vold/ResponseCode.h"
+
+. "$topsrcdir/b2g/config/mozconfigs/common.override"
diff --git a/b2g/config/mozconfigs/linux32_gecko/nightly b/b2g/config/mozconfigs/linux32_gecko/nightly
index 22ba1ef76630f..fac17ee247665 100644
--- a/b2g/config/mozconfigs/linux32_gecko/nightly
+++ b/b2g/config/mozconfigs/linux32_gecko/nightly
@@ -38,3 +38,5 @@ ac_add_options --enable-application=b2g
 ENABLE_MARIONETTE=1
 ac_add_options --disable-elf-hack
 export CXXFLAGS=-DMOZ_ENABLE_JS_DUMP
+
+. "$topsrcdir/b2g/config/mozconfigs/common.override"
diff --git a/b2g/config/mozconfigs/linux64_gecko/nightly b/b2g/config/mozconfigs/linux64_gecko/nightly
index fd23729b96df0..729392f896548 100644
--- a/b2g/config/mozconfigs/linux64_gecko/nightly
+++ b/b2g/config/mozconfigs/linux64_gecko/nightly
@@ -38,3 +38,5 @@ ac_add_options --enable-application=b2g
 ENABLE_MARIONETTE=1
 ac_add_options --disable-elf-hack
 export CXXFLAGS=-DMOZ_ENABLE_JS_DUMP
+
+. "$topsrcdir/b2g/config/mozconfigs/common.override"
diff --git a/b2g/config/mozconfigs/macosx64_gecko/nightly b/b2g/config/mozconfigs/macosx64_gecko/nightly
index 642f75cdcaf51..6f46e34736253 100644
--- a/b2g/config/mozconfigs/macosx64_gecko/nightly
+++ b/b2g/config/mozconfigs/macosx64_gecko/nightly
@@ -26,3 +26,5 @@ ac_add_options --with-ccache
 ENABLE_MARIONETTE=1
 
 export CXXFLAGS=-DMOZ_ENABLE_JS_DUMP
+
+. "$topsrcdir/b2g/config/mozconfigs/common.override"
diff --git a/b2g/config/mozconfigs/win32_gecko/nightly b/b2g/config/mozconfigs/win32_gecko/nightly
index 1a2145ab00d68..1df3057d3e913 100644
--- a/b2g/config/mozconfigs/win32_gecko/nightly
+++ b/b2g/config/mozconfigs/win32_gecko/nightly
@@ -29,3 +29,5 @@ ac_add_options --enable-application=b2g
 ENABLE_MARIONETTE=1
 
 export CXXFLAGS=-DMOZ_ENABLE_JS_DUMP
+
+. "$topsrcdir/b2g/config/mozconfigs/common.override"
diff --git a/browser/config/mozconfigs/linux32/debug b/browser/config/mozconfigs/linux32/debug
index 289923261d0a3..0f8456154aef4 100644
--- a/browser/config/mozconfigs/linux32/debug
+++ b/browser/config/mozconfigs/linux32/debug
@@ -22,3 +22,5 @@ ac_add_options --enable-warnings-as-errors
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/linux32/debug-asan b/browser/config/mozconfigs/linux32/debug-asan
index 2b786c448f5ba..204c2621b335d 100644
--- a/browser/config/mozconfigs/linux32/debug-asan
+++ b/browser/config/mozconfigs/linux32/debug-asan
@@ -16,3 +16,5 @@ mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/linux32/l10n-mozconfig b/browser/config/mozconfigs/linux32/l10n-mozconfig
index 51bb2ee1f6383..0b216be44508a 100644
--- a/browser/config/mozconfigs/linux32/l10n-mozconfig
+++ b/browser/config/mozconfigs/linux32/l10n-mozconfig
@@ -5,3 +5,5 @@ ac_add_options --enable-update-packaging
 
 . $topsrcdir/build/unix/mozconfig.linux
 
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/linux32/nightly b/browser/config/mozconfigs/linux32/nightly
index e8e948426e2f0..18b7160a32806 100644
--- a/browser/config/mozconfigs/linux32/nightly
+++ b/browser/config/mozconfigs/linux32/nightly
@@ -36,3 +36,5 @@ ac_add_options --with-ccache=/usr/bin/ccache
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/linux32/nightly-asan b/browser/config/mozconfigs/linux32/nightly-asan
index 3ea16924a6ea5..1d6037e68c850 100644
--- a/browser/config/mozconfigs/linux32/nightly-asan
+++ b/browser/config/mozconfigs/linux32/nightly-asan
@@ -18,3 +18,5 @@ mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/linux32/qt b/browser/config/mozconfigs/linux32/qt
index 0e36f2d084cb9..0c46f626ee56d 100644
--- a/browser/config/mozconfigs/linux32/qt
+++ b/browser/config/mozconfigs/linux32/qt
@@ -26,3 +26,5 @@ ac_add_options --disable-crashreporter
 
 # Treat warnings as errors in directories with FAIL_ON_WARNINGS.
 ac_add_options --enable-warnings-as-errors
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/linux32/release b/browser/config/mozconfigs/linux32/release
index ebfa65aa17a4d..5927e1cc60469 100644
--- a/browser/config/mozconfigs/linux32/release
+++ b/browser/config/mozconfigs/linux32/release
@@ -24,3 +24,5 @@ mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/linux32/rpm b/browser/config/mozconfigs/linux32/rpm
index 67ea4f27b23d1..9016a2204657f 100644
--- a/browser/config/mozconfigs/linux32/rpm
+++ b/browser/config/mozconfigs/linux32/rpm
@@ -29,3 +29,5 @@ ac_add_options --with-ccache=/usr/bin/ccache
 
 # Treat warnings as errors in directories with FAIL_ON_WARNINGS.
 ac_add_options --enable-warnings-as-errors
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/linux64/debug b/browser/config/mozconfigs/linux64/debug
index 0ad78c09a13ef..d628cb9e2b5d3 100644
--- a/browser/config/mozconfigs/linux64/debug
+++ b/browser/config/mozconfigs/linux64/debug
@@ -22,3 +22,5 @@ ac_add_options --enable-warnings-as-errors
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/linux64/debug-asan b/browser/config/mozconfigs/linux64/debug-asan
index 2b786c448f5ba..204c2621b335d 100644
--- a/browser/config/mozconfigs/linux64/debug-asan
+++ b/browser/config/mozconfigs/linux64/debug-asan
@@ -16,3 +16,5 @@ mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/linux64/l10n-mozconfig b/browser/config/mozconfigs/linux64/l10n-mozconfig
index 51bb2ee1f6383..0b216be44508a 100644
--- a/browser/config/mozconfigs/linux64/l10n-mozconfig
+++ b/browser/config/mozconfigs/linux64/l10n-mozconfig
@@ -5,3 +5,5 @@ ac_add_options --enable-update-packaging
 
 . $topsrcdir/build/unix/mozconfig.linux
 
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/linux64/nightly b/browser/config/mozconfigs/linux64/nightly
index e8e948426e2f0..18b7160a32806 100644
--- a/browser/config/mozconfigs/linux64/nightly
+++ b/browser/config/mozconfigs/linux64/nightly
@@ -36,3 +36,5 @@ ac_add_options --with-ccache=/usr/bin/ccache
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/linux64/nightly-asan b/browser/config/mozconfigs/linux64/nightly-asan
index 3ea16924a6ea5..1d6037e68c850 100644
--- a/browser/config/mozconfigs/linux64/nightly-asan
+++ b/browser/config/mozconfigs/linux64/nightly-asan
@@ -18,3 +18,5 @@ mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/linux64/release b/browser/config/mozconfigs/linux64/release
index ebfa65aa17a4d..5927e1cc60469 100644
--- a/browser/config/mozconfigs/linux64/release
+++ b/browser/config/mozconfigs/linux64/release
@@ -24,3 +24,5 @@ mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/linux64/rpm b/browser/config/mozconfigs/linux64/rpm
index 54cb22262b73c..11a24f518559e 100644
--- a/browser/config/mozconfigs/linux64/rpm
+++ b/browser/config/mozconfigs/linux64/rpm
@@ -29,3 +29,5 @@ ac_add_options --with-ccache=/usr/bin/ccache
 
 # Treat warnings as errors in directories with FAIL_ON_WARNINGS.
 ac_add_options --enable-warnings-as-errors
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/macosx-universal/nightly b/browser/config/mozconfigs/macosx-universal/nightly
index 43ed34512f5e4..0869abc52df9a 100644
--- a/browser/config/mozconfigs/macosx-universal/nightly
+++ b/browser/config/mozconfigs/macosx-universal/nightly
@@ -26,3 +26,5 @@ ac_add_options --enable-warnings-as-errors
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/macosx-universal/release b/browser/config/mozconfigs/macosx-universal/release
index f8b2c2925e2a2..47e0b185ef80f 100644
--- a/browser/config/mozconfigs/macosx-universal/release
+++ b/browser/config/mozconfigs/macosx-universal/release
@@ -20,3 +20,5 @@ mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/macosx-universal/shark b/browser/config/mozconfigs/macosx-universal/shark
index 48f355dbe1b14..1132260ef908f 100644
--- a/browser/config/mozconfigs/macosx-universal/shark
+++ b/browser/config/mozconfigs/macosx-universal/shark
@@ -24,3 +24,5 @@ export MOZ_PKG_SPECIAL="shark"
 # Treat warnings as errors in directories with FAIL_ON_WARNINGS.
 ac_add_options --enable-warnings-as-errors
 ac_add_options --with-ccache
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/macosx32/debug b/browser/config/mozconfigs/macosx32/debug
index f8cbd2d189aad..1e6fcaa00ab13 100644
--- a/browser/config/mozconfigs/macosx32/debug
+++ b/browser/config/mozconfigs/macosx32/debug
@@ -15,3 +15,5 @@ ac_add_options --with-macbundlename-prefix=Firefox
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/macosx64/debug b/browser/config/mozconfigs/macosx64/debug
index eeb39c5e2f436..bc7a6f720d57f 100644
--- a/browser/config/mozconfigs/macosx64/debug
+++ b/browser/config/mozconfigs/macosx64/debug
@@ -19,3 +19,5 @@ ac_add_options --enable-warnings-as-errors
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/macosx64/debug-asan b/browser/config/mozconfigs/macosx64/debug-asan
index 1ffc882d4dda4..c9d12ff5d8398 100644
--- a/browser/config/mozconfigs/macosx64/debug-asan
+++ b/browser/config/mozconfigs/macosx64/debug-asan
@@ -12,3 +12,5 @@ mk_add_options MOZ_MAKE_FLAGS="-j12"
 export MOZ_PACKAGE_JSSHELL=1
 
 ac_add_options --with-macbundlename-prefix=Firefox
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/macosx64/l10n-mozconfig b/browser/config/mozconfigs/macosx64/l10n-mozconfig
index e9b68e1b29797..1a2fa3b3fc5db 100644
--- a/browser/config/mozconfigs/macosx64/l10n-mozconfig
+++ b/browser/config/mozconfigs/macosx64/l10n-mozconfig
@@ -5,3 +5,5 @@ ac_add_options --enable-official-branding
 ac_add_options --enable-update-channel=${MOZ_UPDATE_CHANNEL}
 ac_add_options --enable-update-packaging
 ac_add_options --with-ccache
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/win32/debug b/browser/config/mozconfigs/win32/debug
index 3ddbc441d7114..195b5232a4e0a 100644
--- a/browser/config/mozconfigs/win32/debug
+++ b/browser/config/mozconfigs/win32/debug
@@ -22,3 +22,5 @@ fi
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/win32/l10n-mozconfig b/browser/config/mozconfigs/win32/l10n-mozconfig
index 5ac1722dddbcd..9af0999e73f2a 100644
--- a/browser/config/mozconfigs/win32/l10n-mozconfig
+++ b/browser/config/mozconfigs/win32/l10n-mozconfig
@@ -10,3 +10,5 @@ if test "$PROCESSOR_ARCHITECTURE" = "AMD64" -o "$PROCESSOR_ARCHITEW6432" = "AMD6
 else
   . $topsrcdir/build/win32/mozconfig.vs2010
 fi
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/win32/nightly b/browser/config/mozconfigs/win32/nightly
index 1d2c9683b6d7f..ceca298368c0a 100644
--- a/browser/config/mozconfigs/win32/nightly
+++ b/browser/config/mozconfigs/win32/nightly
@@ -31,3 +31,5 @@ fi
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/win32/release b/browser/config/mozconfigs/win32/release
index 53f1f91fb373c..ef29efc270827 100644
--- a/browser/config/mozconfigs/win32/release
+++ b/browser/config/mozconfigs/win32/release
@@ -28,3 +28,5 @@ fi
 
 # Package js shell.
 export MOZ_PACKAGE_JSSHELL=1
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/win64/debug b/browser/config/mozconfigs/win64/debug
index 444adfcd2f615..c22830b82e6e5 100644
--- a/browser/config/mozconfigs/win64/debug
+++ b/browser/config/mozconfigs/win64/debug
@@ -15,3 +15,5 @@ mk_add_options MOZ_MAKE_FLAGS=-j1
 export MOZ_PACKAGE_JSSHELL=1
 
 . $topsrcdir/build/win64/mozconfig.vs2010
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/browser/config/mozconfigs/win64/nightly b/browser/config/mozconfigs/win64/nightly
index de6ab34ce6de1..5e77d12cfaa43 100644
--- a/browser/config/mozconfigs/win64/nightly
+++ b/browser/config/mozconfigs/win64/nightly
@@ -24,3 +24,5 @@ mk_add_options MOZ_MAKE_FLAGS=-j1
 export MOZ_PACKAGE_JSSHELL=1
 
 . $topsrcdir/build/win64/mozconfig.vs2010
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/build/mozconfig.common b/build/mozconfig.common
index f8f4c0ebe20d3..1dfff9deeb26d 100644
--- a/build/mozconfig.common
+++ b/build/mozconfig.common
@@ -6,4 +6,6 @@
 #
 # Add options to this file that will be inherited by all in-tree mozconfigs.
 # This is useful for eg try builds with nondefault options that apply to all
-# architectures.
+# architectures, though note that if you want to override options set in
+# another mozconfig file, you'll need to use mozconfig.common.override instead
+# of this file.
diff --git a/build/mozconfig.common.override b/build/mozconfig.common.override
new file mode 100644
index 0000000000000..7285aa9ddebd4
--- /dev/null
+++ b/build/mozconfig.common.override
@@ -0,0 +1,11 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# Common mozconfig for all users
+#
+# Add options to this file that will be inherited by all in-tree mozconfigs.
+# This file is included at the *end* of the mozconfigs, and so may be used
+# to override anything done previously.
+#
+# The common expected usage is for try builds with nondefault options.
diff --git a/mobile/android/config/mozconfigs/common b/mobile/android/config/mozconfigs/common
index 6f85fecad7ab1..81e7a8da75ae3 100644
--- a/mobile/android/config/mozconfigs/common
+++ b/mobile/android/config/mozconfigs/common
@@ -2,6 +2,6 @@
 # License, v. 2.0. If a copy of the MPL was not distributed with this
 # file, You can obtain one at http://mozilla.org/MPL/2.0/.
 
-# This file is included by all native android mozconfigs
+# This file is included at the top of all native android mozconfigs
 
 . "$topsrcdir/build/mozconfig.common"
diff --git a/mobile/android/config/mozconfigs/common.override b/mobile/android/config/mozconfigs/common.override
new file mode 100644
index 0000000000000..97b47ae0aa490
--- /dev/null
+++ b/mobile/android/config/mozconfigs/common.override
@@ -0,0 +1,7 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file is included at the bottom of all native android mozconfigs
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/mobile/xul/config/mozconfigs/android/common b/mobile/xul/config/mozconfigs/android/common
index 837211977a687..5d3bb455995c7 100644
--- a/mobile/xul/config/mozconfigs/android/common
+++ b/mobile/xul/config/mozconfigs/android/common
@@ -1 +1,7 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file is included at the top of all Android XUL mozconfigs
+
 . "$topsrcdir/build/mozconfig.common"
diff --git a/mobile/xul/config/mozconfigs/android/common.override b/mobile/xul/config/mozconfigs/android/common.override
new file mode 100644
index 0000000000000..4612266b6cf5a
--- /dev/null
+++ b/mobile/xul/config/mozconfigs/android/common.override
@@ -0,0 +1,7 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file is included at the bottom of all Android XUL mozconfigs
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/mobile/xul/config/mozconfigs/android/debug b/mobile/xul/config/mozconfigs/android/debug
index 973e5b53c4c0e..548d68804435a 100644
--- a/mobile/xul/config/mozconfigs/android/debug
+++ b/mobile/xul/config/mozconfigs/android/debug
@@ -22,3 +22,5 @@ ac_add_options --with-branding=mobile/xul/branding/nightly
 
 # Treat warnings as errors in directories with FAIL_ON_WARNINGS.
 ac_add_options --enable-warnings-as-errors
+
+. "$topsrcdir/mobile/xul/config/mozconfigs/android/common.override"
diff --git a/mobile/xul/config/mozconfigs/android/nightly b/mobile/xul/config/mozconfigs/android/nightly
index 6f6c3d79e9d55..12a86eeb2b00f 100644
--- a/mobile/xul/config/mozconfigs/android/nightly
+++ b/mobile/xul/config/mozconfigs/android/nightly
@@ -25,3 +25,5 @@ ac_add_options --with-branding=mobile/xul/branding/nightly
 
 # Treat warnings as errors in directories with FAIL_ON_WARNINGS.
 ac_add_options --enable-warnings-as-errors
+
+. "$topsrcdir/mobile/xul/config/mozconfigs/android/common.override"
diff --git a/mobile/xul/config/mozconfigs/android/release b/mobile/xul/config/mozconfigs/android/release
index d90f393ede80a..40ba4aa9f2e4e 100644
--- a/mobile/xul/config/mozconfigs/android/release
+++ b/mobile/xul/config/mozconfigs/android/release
@@ -21,3 +21,5 @@ export MOZ_TELEMETRY_REPORTING=1
 
 ac_add_options --enable-official-branding
 ac_add_options --with-branding=mobile/xul/branding/beta
+
+. "$topsrcdir/mobile/xul/config/mozconfigs/android/common.override"
diff --git a/xulrunner/config/mozconfigs/common b/xulrunner/config/mozconfigs/common
index 837211977a687..a6811c575c944 100644
--- a/xulrunner/config/mozconfigs/common
+++ b/xulrunner/config/mozconfigs/common
@@ -1 +1,7 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file is included at the top of all xulrunner mozconfigs
+
 . "$topsrcdir/build/mozconfig.common"
diff --git a/xulrunner/config/mozconfigs/common.override b/xulrunner/config/mozconfigs/common.override
new file mode 100644
index 0000000000000..2663d3baf58be
--- /dev/null
+++ b/xulrunner/config/mozconfigs/common.override
@@ -0,0 +1,7 @@
+# This Source Code Form is subject to the terms of the Mozilla Public
+# License, v. 2.0. If a copy of the MPL was not distributed with this
+# file, You can obtain one at http://mozilla.org/MPL/2.0/.
+
+# This file is included at the bottom of all xulrunner mozconfigs
+
+. "$topsrcdir/build/mozconfig.common.override"
diff --git a/xulrunner/config/mozconfigs/linux32/xulrunner b/xulrunner/config/mozconfigs/linux32/xulrunner
index bab76aeaf13d2..2c78ce8d2e986 100644
--- a/xulrunner/config/mozconfigs/linux32/xulrunner
+++ b/xulrunner/config/mozconfigs/linux32/xulrunner
@@ -14,3 +14,5 @@ mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 #Use ccache
 ac_add_options --with-ccache=/usr/bin/ccache
+
+. "$topsrcdir/xulrunner/config/mozconfigs/common.override"
diff --git a/xulrunner/config/mozconfigs/linux32/xulrunner-qt b/xulrunner/config/mozconfigs/linux32/xulrunner-qt
index f3a53fde16f14..c5b020637862c 100644
--- a/xulrunner/config/mozconfigs/linux32/xulrunner-qt
+++ b/xulrunner/config/mozconfigs/linux32/xulrunner-qt
@@ -20,3 +20,5 @@ export PKG_CONFIG_PATH=/tools/qt-4.6.3/qt/lib/pkgconfig
 ac_add_options --with-qtdir=/tools/qt-4.6.3/qt
 ac_add_options --enable-default-toolkit=cairo-qt
 ac_add_options --disable-crashreporter
+
+. "$topsrcdir/xulrunner/config/mozconfigs/common.override"
diff --git a/xulrunner/config/mozconfigs/linux64/xulrunner b/xulrunner/config/mozconfigs/linux64/xulrunner
index bab76aeaf13d2..2c78ce8d2e986 100644
--- a/xulrunner/config/mozconfigs/linux64/xulrunner
+++ b/xulrunner/config/mozconfigs/linux64/xulrunner
@@ -14,3 +14,5 @@ mk_add_options MOZ_MAKE_FLAGS="-j4"
 
 #Use ccache
 ac_add_options --with-ccache=/usr/bin/ccache
+
+. "$topsrcdir/xulrunner/config/mozconfigs/common.override"
diff --git a/xulrunner/config/mozconfigs/macosx-universal/xulrunner b/xulrunner/config/mozconfigs/macosx-universal/xulrunner
index 76c5620aca125..a864cc9f34935 100644
--- a/xulrunner/config/mozconfigs/macosx-universal/xulrunner
+++ b/xulrunner/config/mozconfigs/macosx-universal/xulrunner
@@ -7,3 +7,5 @@ ac_add_options --disable-tests
 
 # Enable parallel compiling
 mk_add_options MOZ_MAKE_FLAGS="-j4"
+
+. "$topsrcdir/xulrunner/config/mozconfigs/common.override"
diff --git a/xulrunner/config/mozconfigs/win32/xulrunner b/xulrunner/config/mozconfigs/win32/xulrunner
index 09c4727b3c34c..695656a56def4 100644
--- a/xulrunner/config/mozconfigs/win32/xulrunner
+++ b/xulrunner/config/mozconfigs/win32/xulrunner
@@ -14,3 +14,5 @@ if test "$PROCESSOR_ARCHITECTURE" = "AMD64" -o "$PROCESSOR_ARCHITEW6432" = "AMD6
 else
   . $topsrcdir/build/win32/mozconfig.vs2010
 fi
+
+. "$topsrcdir/xulrunner/config/mozconfigs/common.override"
diff --git a/xulrunner/config/mozconfigs/win64/xulrunner b/xulrunner/config/mozconfigs/win64/xulrunner
index 596c2729db3f3..303c7e6e45f41 100644
--- a/xulrunner/config/mozconfigs/win64/xulrunner
+++ b/xulrunner/config/mozconfigs/win64/xulrunner
@@ -11,3 +11,5 @@ ac_add_options --enable-jemalloc
 ac_add_options --disable-tests
 
 mk_add_options MOZ_MAKE_FLAGS=-j1
+
+. "$topsrcdir/xulrunner/config/mozconfigs/common.override"