diff --git a/lib/types/multipart.js b/lib/types/multipart.js
index b6d8e8b..6390518 100644
--- a/lib/types/multipart.js
+++ b/lib/types/multipart.js
@@ -12,7 +12,8 @@ var Dicer = require('dicer');
 
 var parseParams = require('../utils').parseParams,
     decodeText = require('../utils').decodeText,
-    basename = require('../utils').basename;
+    basename = require('../utils').basename,
+    getLimit = require('../utils').getLimit;
 
 var RE_BOUNDARY = /^boundary$/i,
     RE_FIELD = /^form-data$/i,
@@ -57,21 +58,11 @@ function Multipart(boy, cfg) {
   if (typeof boundary !== 'string')
     throw new Error('Multipart: Boundary not found');
 
-  var fieldSizeLimit = (limits && typeof limits.fieldSize === 'number'
-                        ? limits.fieldSize
-                        : 1 * 1024 * 1024),
-      fileSizeLimit = (limits && typeof limits.fileSize === 'number'
-                       ? limits.fileSize
-                       : Infinity),
-      filesLimit = (limits && typeof limits.files === 'number'
-                    ? limits.files
-                    : Infinity),
-      fieldsLimit = (limits && typeof limits.fields === 'number'
-                     ? limits.fields
-                     : Infinity),
-      partsLimit = (limits && typeof limits.parts === 'number'
-                    ? limits.parts
-                    : Infinity);
+  var fieldSizeLimit = getLimit(limits, 'fieldSize', 1 * 1024 * 1024),
+      fileSizeLimit = getLimit(limits, 'fileSize', Infinity),
+      filesLimit = getLimit(limits, 'files', Infinity),
+      fieldsLimit = getLimit(limits, 'fields', Infinity),
+      partsLimit = getLimit(limits, 'parts', Infinity);
 
   var nfiles = 0,
       nfields = 0,
diff --git a/lib/types/urlencoded.js b/lib/types/urlencoded.js
index 361c804..0f61330 100644
--- a/lib/types/urlencoded.js
+++ b/lib/types/urlencoded.js
@@ -1,5 +1,6 @@
 var Decoder = require('../utils').Decoder,
-    decodeText = require('../utils').decodeText;
+    decodeText = require('../utils').decodeText,
+    getLimit = require('../utils').getLimit;
 
 var RE_CHARSET = /^charset$/i;
 
@@ -12,15 +13,9 @@ function UrlEncoded(boy, cfg) {
       parsedConType = cfg.parsedConType;
   this.boy = boy;
 
-  this.fieldSizeLimit = (limits && typeof limits.fieldSize === 'number'
-                         ? limits.fieldSize
-                         : 1 * 1024 * 1024);
-  this.fieldNameSizeLimit = (limits && typeof limits.fieldNameSize === 'number'
-                             ? limits.fieldNameSize
-                             : 100);
-  this.fieldsLimit = (limits && typeof limits.fields === 'number'
-                      ? limits.fields
-                      : Infinity);
+  this.fieldSizeLimit = getLimit(limits, 'fieldSize', 1 * 1024 * 1024);
+  this.fieldNameSizeLimit = getLimit(limits, 'fieldNameSize', 100);
+  this.fieldsLimit = getLimit(limits, 'fields', Infinity);
 
   var charset;
   for (var i = 0, len = parsedConType.length; i < len; ++i) {
diff --git a/lib/utils.js b/lib/utils.js
index 57d745f..c2a0f9d 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -170,3 +170,22 @@ function basename(path) {
   return (path === '..' || path === '.' ? '' : path);
 }
 exports.basename = basename;
+
+
+function getLimit(limits, name, defaultLimit) {
+  if (!limits)
+    return defaultLimit;
+
+  var limit = limits[name];
+  // Intentional double equals
+  if (limit == undefined)
+    return defaultLimit;
+
+  // Ensure limit is a number and is not NaN
+  if (typeof limit !== 'number' || limit !== limit) {
+    throw new Error('Limit ' + name + ' is not a valid number');
+  }
+
+  return limit;
+}
+exports.getLimit = getLimit;
diff --git a/test/test-utils-get-limit.js b/test/test-utils-get-limit.js
new file mode 100644
index 0000000..2d1c7fe
--- /dev/null
+++ b/test/test-utils-get-limit.js
@@ -0,0 +1,22 @@
+var getLimit = require('../lib/utils').getLimit;
+
+var assert = require('assert');
+
+assert.strictEqual(getLimit(undefined, 'fieldSize', 1), 1);
+assert.strictEqual(getLimit(undefined, 'fileSize', Infinity), Infinity);
+
+assert.strictEqual(getLimit({}, 'fieldSize', 1), 1);
+assert.strictEqual(getLimit({}, 'fileSize', Infinity), Infinity);
+assert.strictEqual(getLimit({ fieldSize: null }, 'fieldSize', 1), 1);
+assert.strictEqual(getLimit({ fileSize: null }, 'fileSize', Infinity), Infinity);
+
+assert.strictEqual(getLimit({ fieldSize: 0 }, 'fieldSize', 1), 0);
+assert.strictEqual(getLimit({ fileSize: 2 }, 'fileSize', 1), 2);
+
+assert.throws(function() {
+  getLimit({ fieldSize: '1' }, 'fieldSize', 1);
+}, /^Error: Limit fieldSize is not a valid number$/);
+
+assert.throws(function() {
+  getLimit({ fieldSize: NaN }, 'fieldSize', 1);
+}, /^Error: Limit fieldSize is not a valid number$/);