Check for self.req existence inside the write method

request.js

@@ -1382,7 +1382,9 @@ Request.prototype.write = function () {
   if (!self._started) {
     self.start()
   }
-  return self.req.write.apply(self.req, arguments)
+  if (self.req) {
+    return self.req.write.apply(self.req, arguments)
+  }
 }
 Request.prototype.end = function (chunk) {
   var self = this

tests/test-headers.js

@@ -162,7 +162,7 @@ tape('undefined headers', function(t) {
   })
 })
 
-tape('catch invalid characters error', function(t) {
+tape('catch invalid characters error - GET', function(t) {
   request({
     url: s.url + '/headers.json',
     headers: {
@@ -177,6 +177,23 @@ tape('catch invalid characters error', function(t) {
   })
 })
 
+tape('catch invalid characters error - POST', function(t) {
+  request({
+    method: 'POST',
+    url: s.url + '/headers.json',
+    headers: {
+      'test': 'אבגד'
+    },
+    body: 'beep'
+  }, function(err, res, body) {
+    t.equal(err.message, 'The header content contains invalid characters')
+  })
+  .on('error', function (err) {
+    t.equal(err.message, 'The header content contains invalid characters')
+    t.end()
+  })
+})
+
 tape('cleanup', function(t) {
   s.close(function() {
     t.end()