--- a/build/moz.configure/ffi.configure
+++ b/build/moz.configure/ffi.configure
@@ -2,17 +2,17 @@
 # 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/.
 
 @depends(target)
 def force_system_ffi(target):
     # Pre-emptively move to system ffi for non-tier one platforms.
-    if target.cpu not in ('x86', 'x86_64', 'arm'):
+    if target.cpu not in ('x86', 'x86_64', 'arm', 'aarch64'):
         return True
 
 imply_option('--with-system-ffi', force_system_ffi, "target")
 
 js_option('--with-system-ffi',
           help='Use system libffi (located with pkgconfig)')
 
 use_system_ffi = depends_if('--with-system-ffi')(lambda _: True)
@@ -23,32 +23,35 @@ system_ffi = pkg_check_modules('MOZ_FFI'
 building_ffi = depends(system_ffi)(lambda v: not bool(v))
 
 set_config('MOZ_SYSTEM_FFI', system_ffi)
 add_old_configure_assignment('MOZ_SYSTEM_FFI', system_ffi)
 
 # Target selection, based on ffi/configure.ac.
 @depends_when(target, when=building_ffi)
 def ffi_target(target):
-    if target.cpu not in ('x86', 'x86_64', 'arm'):
+    if target.cpu not in ('x86', 'x86_64', 'arm', 'aarch64'):
         die('Building libffi from the tree is not supported on this platform. '
             'Use --with-system-ffi instead.')
 
     if target.os == 'WINNT':
         target_dir = 'x86'
         if target.cpu == 'x86_64':
             target_name = 'X86_WIN64'
         else:
             target_name = 'X86_WIN32'
     elif target.os == 'OSX':
         target_dir = 'x86'
         target_name = 'X86_DARWIN'
     elif target.cpu == 'arm':
         target_dir = 'arm'
         target_name = 'ARM'
+    elif target.cpu == 'aarch64':
+        target_dir = 'aarch64'
+        target_name = 'AARCH64'
     else:
         target_dir = 'x86'
         target_name = target.cpu.upper()
 
     return namespace(
         name=target_name,
         dir=target_dir
     )

--- a/config/external/ffi/moz.build
+++ b/config/external/ffi/moz.build
@@ -72,16 +72,18 @@ else:
     ]
 
     # Per-platform sources and flags.
     ffi_srcs = ()
     if CONFIG['FFI_TARGET'] == 'ARM':
         ffi_srcs = ('sysv.S', 'ffi.c')
         if CONFIG['CLANG_CXX']:
             ASFLAGS += ['-no-integrated-as']
+    elif CONFIG['FFI_TARGET'] == 'AARCH64':
+        ffi_srcs = ('sysv.S', 'ffi.c')
     elif CONFIG['FFI_TARGET'] == 'X86':
         ffi_srcs = ('ffi.c', 'sysv.S', 'win32.S')
     elif CONFIG['FFI_TARGET'] == 'X86_64':
         ffi_srcs = ('ffi64.c', 'unix64.S', 'ffi.c', 'sysv.S')
     elif CONFIG['FFI_TARGET'] == 'X86_WIN32':
         ffi_srcs = ('ffi.c', 'win32.S')
     elif CONFIG['FFI_TARGET'] == 'X86_WIN64':
         ffi_srcs = ('ffi.c', 'win64.S')