--- a/security/nss/lib/freebl/freebl.gyp
+++ b/security/nss/lib/freebl/freebl.gyp
@@ -401,16 +401,21 @@
           [ 'target_arch=="arm"', {
             'defines': [
               'MP_ASSEMBLY_MULTIPLY',
               'MP_ASSEMBLY_SQUARE',
               'MP_USE_UINT_DIGIT',
               'SHA_NO_LONG_LONG',
             ],
           }],
+          [ 'target_arch=="arm64"', {
+            'defines': [
+              'NSS_USE_64',
+            ],
+          }],
         ],
       }],
     ],
   },
   'variables': {
     'module': 'nss',
   }
 }