diff --git a/lib/main.js b/lib/main.js
index 5702223..a9c95a4 100644
--- a/lib/main.js
+++ b/lib/main.js
@@ -5,6 +5,9 @@ const parseParams = require('./utils').parseParams
 
 function Busboy (opts) {
   if (!(this instanceof Busboy)) { return new Busboy(opts) }
+  if (typeof opts !== 'object') {
+    throw new TypeError('Busboy expected an options-Object.')
+  }
   if (opts.highWaterMark !== undefined) { WritableStream.call(this, { autoDestroy: false, highWaterMark: opts.highWaterMark }) } else { WritableStream.call(this, { autoDestroy: false }) }
 
   this._done = false
@@ -32,7 +35,7 @@ Busboy.prototype.emit = function (ev) {
 Busboy.prototype.parseHeaders = function (headers) {
   this._parser = undefined
   if (headers['content-type']) {
-    const parsed = parseParams(headers['content-type'])
+    const parsed = parseParams(headers['content-type'], this.opts.limits || {})
     let matched; let type
     for (var i = 0; i < TYPES.length; ++i) { // eslint-disable-line no-var
       type = TYPES[i]
diff --git a/lib/types/multipart.js b/lib/types/multipart.js
index ac8b022..cfbe41b 100644
--- a/lib/types/multipart.js
+++ b/lib/types/multipart.js
@@ -2,8 +2,6 @@
 //  * support 1 nested multipart level
 //    (see second multipart example here:
 //     http://www.w3.org/TR/html401/interact/forms.html#didx-multipartform-data)
-//  * support limits.fieldNameSize
-//     -- this will require modifications to utils.parseParams
 
 const ReadableStream = require('stream').Readable
 const inherits = require('util').inherits
@@ -135,7 +133,7 @@ function Multipart (boy, cfg) {
       if (charset === undefined) { charset = defCharset }
 
       if (header['content-disposition']) {
-        parsed = parseParams(header['content-disposition'][0])
+        parsed = parseParams(header['content-disposition'][0], limits)
         if (!RE_FIELD.test(parsed[0])) { return skipPart(part) }
         for (i = 0, len = parsed.length; i < len; ++i) {
           if (RE_NAME.test(parsed[i][0])) {
diff --git a/lib/utils.js b/lib/utils.js
index 7b45211..5948f49 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -4,7 +4,10 @@ const RE_ENCODED = /%([a-fA-F0-9]{2})/g
 function encodedReplacer (match, byte) {
   return String.fromCharCode(parseInt(byte, 16))
 }
-function parseParams (str) {
+
+const rfcSpecificFieldnames = ['name', 'encoding', 'boundary', 'charset', 'filename']
+
+function parseParams (str, options) {
   const res = []
   let state = 'key'
   let charset = ''
@@ -13,12 +16,12 @@ function parseParams (str) {
   let p = 0
   let tmp = ''
 
+  const fieldNameSize = (options && options.fieldNameSize) || Infinity
+
   for (var i = 0, len = str.length; i < len; ++i) { // eslint-disable-line no-var
     if (str[i] === '\\' && inquote) {
-      if (escaping) { escaping = false } else {
-        escaping = true
-        continue
-      }
+      escaping = !escaping
+      continue
     } else if (str[i] === '"') {
       if (!escaping) {
         if (inquote) {
@@ -38,9 +41,15 @@ function parseParams (str) {
         tmp = ''
         continue
       } else if (state === 'key' &&
-                 (str[i] === '*' || str[i] === '=') &&
-                 res.length) {
+        (str[i] === '*' || str[i] === '=') &&
+        res.length) {
         if (str[i] === '*') { state = 'charset' } else { state = 'value' }
+        if (
+          str[i] === '=' &&
+          fieldNameSize !== Infinity &&
+          rfcSpecificFieldnames.indexOf(tmp) === -1) {
+          tmp = tmp.substring(0, fieldNameSize)
+        }
         res[p] = [tmp, undefined]
         tmp = ''
         continue
diff --git a/test/parse-params.spec.js b/test/parse-params.spec.js
index a4a9e4f..67e1ef9 100644
--- a/test/parse-params.spec.js
+++ b/test/parse-params.spec.js
@@ -103,10 +103,18 @@ describe('parse-params', () => {
       source: 'multipart/form-data; charset=utf-8; boundary=0xKhTmLbOuNdArY',
       expected: ['multipart/form-data', ['charset', 'utf-8'], ['boundary', '0xKhTmLbOuNdArY']],
       what: 'Multiple non-quoted parameters'
+    },
+    {
+      options: {
+        fieldNameSize: 2
+      },
+      source: 'text/plain; encoding="utf8";\t   foo=bar;test',
+      expected: ['text/plain', ['encoding', 'utf8'], ['fo', 'bar'], 'test'],
+      what: 'fieldNameSize should be respected'
     }
   ].forEach((v) => {
     it(v.what, () => {
-      const result = parseParams(v.source)
+      const result = parseParams(v.source, v.options)
       const msg = 'parsed parameters mismatch.\n' +
               'Saw: ' + inspect(result) + '\n' +
               'Expected: ' + inspect(v.expected)
diff --git a/test/types-multipart.spec.js b/test/types-multipart.spec.js
index b3dc23d..d6e8220 100644
--- a/test/types-multipart.spec.js
+++ b/test/types-multipart.spec.js
@@ -90,7 +90,8 @@ describe('types-multipart', () => {
       boundary: '---------------------------paZqsnEHRufoShdX6fh0lUhXBP4k',
       limits: {
         fileSize: 13,
-        fieldSize: 5
+        fieldSize: 5,
+        fieldNameSize: 3
       },
       expected: [
         ['field', 'file_name_0', 'super', false, true, '7bit', 'text/plain'],