diff --git a/src/lib/string_set.js b/src/lib/string_set.js
index bac46526b..9d03d40d1 100644
--- a/src/lib/string_set.js
+++ b/src/lib/string_set.js
@@ -1,37 +1,54 @@
 function StringSet(items) {
   this._items = {};
+  this._nums = {};
   this._length = items ? items.length : 0;
   if (!items) return;
   for (let i = 0, l = items.length; i < l; i++) {
+    this.add(items[i]);
     if (items[i] === undefined) continue;
-    this._items[items[i]] = i;
+    if (typeof items[i] === 'string') this._items[items[i]] = i;
+    else this._nums[items[i]] = i;
+
   }
 }
 
 StringSet.prototype.add = function(x) {
-  this._length = this._items[x] ? this._length : this._length + 1;
-  this._items[x] = this._items[x] ? this._items[x] : this._length;
+  if (this.has(x)) return this;
+  this._length++;
+  if (typeof x === 'string') this._items[x] = this._length;
+  else this._nums[x] = this._length;
   return this;
 };
 
 StringSet.prototype.delete = function(x) {
-  this._length = this._items[x] ? this._length - 1 : this._length;
+  if (this.has(x) === false) return this;
+  this._length--;
   delete this._items[x];
+  delete this._nums[x];
   return this;
 };
 
 StringSet.prototype.has = function(x) {
-  return this._items[x] !== undefined;
+  if (typeof x !== 'string' && typeof x !== 'number') return false;
+  return this._items[x] !== undefined || this._nums[x] !== undefined;
 };
 
 StringSet.prototype.values = function() {
-  const orderedKeys = Object.keys(this._items).sort((a, b) => this._items[a] - this._items[b]);
-  return orderedKeys;
+  const values = [];
+  Object.keys(this._items).forEach(k => {
+    values.push({ k: k, v: this._items[k] });
+  });
+  Object.keys(this._nums).forEach(k => {
+    values.push({ k: JSON.parse(k), v: this._nums[k] });
+  });
+
+  return values.sort((a, b) => a.v - b.v).map(a => a.k);
 };
 
 StringSet.prototype.clear = function() {
   this._length = 0;
   this._items = {};
+  this._nums = {};
   return this;
 };
 
diff --git a/test/string_set.test.js b/test/string_set.test.js
index 5c9b3360b..c93b00fb3 100644
--- a/test/string_set.test.js
+++ b/test/string_set.test.js
@@ -13,8 +13,8 @@ test('StringSet constructor and API', t => {
   t.equal(typeof StringSet.prototype.clear, 'function', 'exposes set.clear');
   t.equal(Object.keys(StringSet.prototype).filter(k => k[0] !== '_').length, 5, 'no unexpected methods');
 
-  const populatedSet = new StringSet(['a', 'b']);
-  t.deepEqual(populatedSet.values(), ['a', 'b'], 'populated by constructor arg');
+  const populatedSet = new StringSet(['a', 4, 'b']);
+  t.deepEqual(populatedSet.values(), ['a', 4, 'b'], 'populated by constructor arg');
 
   t.end();
 });
@@ -28,29 +28,35 @@ test('StringSet#add', t => {
   t.deepEqual(set.values(), ['a', 'b']);
   set.add('a');
   t.deepEqual(set.values(), ['a', 'b']);
+  set.add(3);
+  t.deepEqual(set.values(), ['a', 'b', 3]);
   t.end();
 });
 
 test('StringSet#delete', t => {
-  const subject = ['a', 'b'];
+  const subject = ['a', 'b', 2];
   const set = new StringSet(subject);
   set.delete('a');
-  t.deepEqual(set.values(), ['b']);
+  t.deepEqual(set.values(), ['b', 2]);
   set.delete('a');
-  t.deepEqual(set.values(), ['b']);
+  t.deepEqual(set.values(), ['b', 2]);
   set.delete();
-  t.deepEqual(set.values(), ['b']);
+  t.deepEqual(set.values(), ['b', 2]);
   set.delete('b');
+  t.deepEqual(set.values(), [2]);
+  set.delete(2);
   t.deepEqual(set.values(), []);
-  t.deepEqual(subject, ['a', 'b'], 'source array not mutated');
+  t.deepEqual(subject, ['a', 'b', 2], 'source array not mutated');
   t.end();
 });
 
 test('StringSet#has', t => {
-  const set = new StringSet(['a', 'b']);
+  const set = new StringSet(['a', 'b', 2]);
   t.equal(set.has('a'), true);
   t.equal(set.has('b'), true);
+  t.equal(set.has(2), true);
   t.equal(set.has('c'), false);
+  t.equal(set.has(4), false);
   t.end();
 });