Throw if fs start arg is not number

lib/fs.js

@@ -1038,8 +1038,13 @@ var ReadStream = fs.ReadStream = function(path, options) {
   if (this.encoding) this.setEncoding(this.encoding);
 
   if (this.start !== undefined) {
+    if ('number' !== typeof this.start) {
+      throw TypeError("'start' must be a Number or left undefined, not a string containing a number");
+    }
     if (this.end === undefined) {
       this.end = Infinity;
+    } else if ('number' !== typeof this.end) {
+      throw TypeError("'end' must be a Number or left undefined, not a string containing a number");
     }
 
     if (this.start > this.end) {
@@ -1226,6 +1231,9 @@ var WriteStream = fs.WriteStream = function(path, options) {
   }
 
   if (this.start !== undefined) {
+    if ('number' !== typeof this.start) {
+      throw TypeError("'start' must be a Number or left undefined, not a string containing a number");
+    }
     if (this.start < 0) {
       throw new Error('start must be >= zero');
     }

test/simple/test-fs-non-number-arguments-throw.js

@@ -0,0 +1,26 @@
+(function () {
+  "use strict";
+
+  var assert = require('assert'),
+      fs = require('./fs'),
+      saneEmitter;
+
+  saneEmitter = fs.createReadStream(__filename, { start: 17, end: 29 });
+
+  assert.throws(function () {
+    fs.createReadStream(__filename, { start: "17", end: 29 });
+  }, "start as string didn't throw an error for createReadStream");
+
+  assert.throws(function () {
+    fs.createReadStream(__filename, { start: 17, end: "29" });
+  }, "end as string didn't throw an error");
+
+  assert.throws(function () {
+    fs.createWriteStream(__filename, { start: "17" });
+  }, "start as string didn't throw an error for createWriteStream");
+
+  saneEmitter.on('data', function (data) {
+    // a sanity check when using numbers instead of strings
+    assert.strictEqual('"use strict";', data.toString('utf8'), 'read ' + data.toString('utf8') + ' instead of "use strict";');
+  });
+}());