diff --git a/.travis.yml b/.travis.yml
index e2f126e..fb5c778 100644
--- a/.travis.yml
+++ b/.travis.yml
@@ -1,6 +1,7 @@
 language: node_js
 sudo: false
 node_js:
+  - 9
   - 8
   - 7
   - 6
diff --git a/package.json b/package.json
index 21a83c9..85855d0 100644
--- a/package.json
+++ b/package.json
@@ -42,7 +42,7 @@
   "dependencies": {
     "bl": "^1.2.1",
     "inherits": "^2.0.3",
-    "process-nextick-args": "^1.0.7",
+    "process-nextick-args": "^2.0.0",
     "safe-buffer": "^5.1.0"
   }
 }
diff --git a/writeToStream.js b/writeToStream.js
index 99efa14..087763c 100644
--- a/writeToStream.js
+++ b/writeToStream.js
@@ -5,7 +5,7 @@ var Buffer = require('safe-buffer').Buffer
 var empty = Buffer.allocUnsafe(0)
 var zeroBuf = Buffer.from([0])
 var numbers = require('./numbers')
-var nextTick = require('process-nextick-args')
+var nextTick = require('process-nextick-args').nextTick
 
 var numCache = numbers.cache
 var generateNumber = numbers.generateNumber
@@ -584,12 +584,12 @@ function writeStringOrBuffer (stream, toWrite) {
 
 function byteLength (bufOrString) {
   if (!bufOrString) return 0
-  else if (Buffer.isBuffer(bufOrString)) return bufOrString.length
+  else if (bufOrString instanceof Buffer) return bufOrString.length
   else return Buffer.byteLength(bufOrString)
 }
 
 function isStringOrBuffer (field) {
-  return typeof field === 'string' || Buffer.isBuffer(field)
+  return typeof field === 'string' || field instanceof Buffer
 }
 
 module.exports = generate