--- a/b2g/common.configure
+++ b/b2g/common.configure
@@ -20,10 +20,12 @@ set_config('MOZTTDIR', mozttdir)
 
 @depends('MOZTTDIR')
 def package_moztt(value):
     if value:
         return True
 
 set_define('PACKAGE_MOZTT', package_moztt)
 
+imply_option('MOZ_ENABLE_WARNINGS_AS_ERRORS',
+             depends(target)(lambda t: t.os == 'Android'), reason='--target')
 
 include('../toolkit/moz.configure')

--- a/b2g/confvars.sh
+++ b/b2g/confvars.sh
@@ -47,17 +47,13 @@ MOZ_APP_ID={3c2e2abc-06d4-11e1-ac3b-374f
 
 MOZ_TIME_MANAGER=1
 
 MOZ_SIMPLEPUSH=1
 MOZ_PAY=1
 MOZ_TOOLKIT_SEARCH=
 MOZ_B2G=1
 
-if test "$OS_TARGET" = "Android"; then
-MOZ_ENABLE_WARNINGS_AS_ERRORS=1
-fi
-
 MOZ_JSDOWNLOADS=1
 
 MOZ_BUNDLED_FONTS=1
 
 export JS_GC_SMALL_CHUNK_SIZE=1

--- a/b2g/graphene/confvars.sh
+++ b/b2g/graphene/confvars.sh
@@ -42,20 +42,16 @@ fi
 MOZ_APP_ID={d1bfe7d9-c01e-4237-998b-7b5f960a4314}
 MOZ_TIME_MANAGER=1
 
 MOZ_PAY=1
 MOZ_TOOLKIT_SEARCH=
 MOZ_PLACES=
 MOZ_B2G=1
 
-if test "$OS_TARGET" = "Android"; then
-MOZ_ENABLE_WARNINGS_AS_ERRORS=1
-fi
-
 MOZ_JSDOWNLOADS=1
 
 MOZ_BUNDLED_FONTS=1
 
 export JS_GC_SMALL_CHUNK_SIZE=1
 
 # Include the DevTools client, not just the server (which is the default)
 MOZ_DEVTOOLS=all

--- a/build/moz.configure/old.configure
+++ b/build/moz.configure/old.configure
@@ -251,17 +251,16 @@ def old_configure_options(*options):
     '--enable-trace-logging',
     '--enable-tree-freetype',
     '--enable-ui-locale',
     '--enable-universalchardet',
     '--enable-updater',
     '--enable-url-classifier',
     '--enable-valgrind',
     '--enable-verify-mar',
-    '--enable-warnings-as-errors',
     '--enable-webapp-runtime',
     '--enable-webrtc',
     '--enable-websms-backend',
     '--enable-webspeech',
     '--enable-webspeechtestbackend',
     '--enable-xul',
     '--enable-zipwriter',
     '--no-create',

new file mode 100644
--- /dev/null
+++ b/build/moz.configure/warnings.configure
@@ -0,0 +1,12 @@
+# -*- Mode: python; c-basic-offset: 4; indent-tabs-mode: nil; tab-width: 40 -*-
+# vim: set filetype=python:
+# 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/.
+
+option('--enable-warnings-as-errors', env='MOZ_ENABLE_WARNINGS_AS_ERRORS',
+       help='Enable treating warnings as errors')
+
+add_old_configure_assignment(
+    'MOZ_ENABLE_WARNINGS_AS_ERRORS',
+    depends('--enable-warnings-as-errors')(lambda x: bool(x)))

--- a/js/src/old-configure.in
+++ b/js/src/old-configure.in
@@ -508,25 +508,16 @@ if test -n "${CLANG_CC}${CLANG_CL}"; the
 fi
 if test -n "${CLANG_CXX}${CLANG_CL}"; then
     _WARNINGS_CXXFLAGS="-Qunused-arguments ${_WARNINGS_CXXFLAGS}"
 fi
 
 MOZ_CONFIG_SANITIZE
 
 dnl ========================================================
-dnl = Enable treating compiler warnings as errors
-dnl ========================================================
-MOZ_ARG_ENABLE_BOOL(warnings-as-errors,
-[  --enable-warnings-as-errors
-                          Enable treating warnings as errors],
-    MOZ_ENABLE_WARNINGS_AS_ERRORS=1,
-    MOZ_ENABLE_WARNINGS_AS_ERRORS=)
-
-dnl ========================================================
 dnl GNU specific defaults
 dnl ========================================================
 if test "$GNU_CC"; then
     MKSHLIB='$(CXX) $(CXXFLAGS) $(DSO_PIC_CFLAGS) $(DSO_LDOPTS) -Wl,-h,$(DSO_SONAME) -o $@'
     MKCSHLIB='$(CC) $(CFLAGS) $(DSO_PIC_CFLAGS) $(DSO_LDOPTS) -Wl,-h,$(DSO_SONAME) -o $@'
     DSO_LDOPTS='-shared'
     if test "$GCC_USE_GNU_LD"; then
         # Some tools like ASan use a runtime library that is only

--- a/moz.configure
+++ b/moz.configure
@@ -94,16 +94,18 @@ add_old_configure_assignment('MOZ_DEBUG'
                              depends('--enable-debug')(lambda v: bool(v)))
 
 include_when('build/moz.configure/toolchain.configure',
              when='--enable-compile-environment')
 include_when('build/moz.configure/memory.configure',
              when='--enable-compile-environment')
 include_when('build/moz.configure/headers.configure',
              when='--enable-compile-environment')
+include_when('build/moz.configure/warnings.configure',
+             when='--enable-compile-environment')
 
 @depends('--help')
 @imports(_from='mozbuild.backend', _import='backends')
 def build_backends_choices(help):
     return tuple(backends)
 
 
 @deprecated_option('--enable-build-backend', nargs='+',

--- a/old-configure.in
+++ b/old-configure.in
@@ -673,25 +673,16 @@ if test -n "${CLANG_CXX}${CLANG_CL}"; th
     _WARNINGS_CXXFLAGS="-Qunused-arguments ${_WARNINGS_CXXFLAGS}"
 fi
 
 if test -n "$COMPILE_ENVIRONMENT"; then
    MOZ_CONFIG_SANITIZE
 fi
 
 dnl ========================================================
-dnl = Enable treating compiler warnings as errors
-dnl ========================================================
-MOZ_ARG_ENABLE_BOOL(warnings-as-errors,
-[  --enable-warnings-as-errors
-                          Enable treating warnings as errors],
-    MOZ_ENABLE_WARNINGS_AS_ERRORS=1,
-    MOZ_ENABLE_WARNINGS_AS_ERRORS=)
-
-dnl ========================================================
 dnl GNU specific defaults
 dnl ========================================================
 if test "$GNU_CC"; then
     MMX_FLAGS="-mmmx"
     SSE_FLAGS="-msse"
     SSE2_FLAGS="-msse2"
     SSSE3_FLAGS="-mssse3"
     # FIXME: Let us build with strict aliasing. bug 414641.