sfixed64 serialization / deserialization not working properly

[paralin]

var protobufjs = require('protobufjs');
var ro = protobufjs.loadSync('./test.proto');

var test = ro.lookup('test.Test');
var enc = test.encode({int_64: '-9095674951825889465'}).finish();
var dec = test.decode(enc);

if (dec.int_64 === '-9095674951825889465') {
  console.log('Test passed.');
} else {
  console.log(dec.int_64 + ' != -9095674951825889465 (expected)');
}

syntax = "proto3";
package test;

message Test {
  sfixed64 int_64 = 1;
}

Output:

-27182818284590 != -9095674951825889465 (expected)

Extracted from a failing test case in grpc. Tested with both long and no long installed. Node v6.9.1