--- a/build/gyp.mozbuild
+++ b/build/gyp.mozbuild
@@ -79,24 +79,20 @@ flavors = {
     'FreeBSD': 'freebsd',
     'NetBSD': 'netbsd',
     'OpenBSD': 'openbsd',
 }
 gyp_vars['OS'] = flavors[os]
 
 arches = {
     'x86_64': 'x64',
-    'arm': 'arm',
     'x86': 'ia32',
-    'ppc': 'ppc',
-    'ppc64': 'ppc',
-    'ia64': 'ia64',
 }
 
-gyp_vars['target_arch'] = arches[CONFIG['CPU_ARCH']]
+gyp_vars['target_arch'] = arches.get(CONFIG['CPU_ARCH'], CONFIG['CPU_ARCH'])
 
 if CONFIG['ARM_ARCH']:
     if int(CONFIG['ARM_ARCH']) < 7:
         gyp_vars['armv7'] = 0
         gyp_vars['arm_neon_optional'] = 0
     elif os == 'Android':
         gyp_vars['armv7'] = 1
     else: