diff --git a/index.js b/index.js
index dcda631..85c616b 100644
--- a/index.js
+++ b/index.js
@@ -197,7 +197,10 @@ function hash_assign(result, keys, value) {
 
         // If the characters between the brackets is not a number it is an
         // attribute name and can be assigned directly.
-        if (isNaN(index)) {
+        //
+        // If we process the first record and it is non-zero we assume it's a sparse array
+        // and use a hash instead of an array to avoid very large sparse arrays
+        if (isNaN(index) || (result === undefined && index !== 0)) {
             result = result || {};
             result[string] = hash_assign(result[string], keys, value);
         }
diff --git a/package.json b/package.json
index 90361c0..dfb366d 100644
--- a/package.json
+++ b/package.json
@@ -7,6 +7,7 @@
     "test": "test"
   },
   "devDependencies": {
+    "core-assert": "~0.1.3",
     "domify": "~1.4.0",
     "zuul": "~3.10.1"
   },
@@ -27,4 +28,4 @@
   "bugs": {
     "url": "https://github.com/shtylman/form-serialize/issues"
   }
-}
\ No newline at end of file
+}
diff --git a/test/index.js b/test/index.js
index ee2a60a..290087a 100644
--- a/test/index.js
+++ b/test/index.js
@@ -1,10 +1,10 @@
-var assert = require('assert');
+var assert = require('core-assert');
 var domify = require('domify');
 
 var serialize = require('../');
 
 var hash_check = function(form, exp) {
-    assert.deepEqual(serialize(form, { hash: true }), exp);
+    assert.deepStrictEqual(serialize(form, { hash: true }), exp);
 };
 
 var str_check = function(form, exp) {
@@ -12,15 +12,15 @@ var str_check = function(form, exp) {
 };
 
 var disabled_check = function(form, exp) {
-    assert.deepEqual(serialize(form, { hash : false, disabled: true }), exp);
+    assert.deepStrictEqual(serialize(form, { hash : false, disabled: true }), exp);
 };
 
 var empty_check = function(form, exp) {
-    assert.deepEqual(serialize(form, { hash : false, disabled: true, empty: true }), exp);
+    assert.deepStrictEqual(serialize(form, { hash : false, disabled: true, empty: true }), exp);
 };
 
 var empty_check_hash = function(form, exp) {
-    assert.deepEqual(serialize(form, { hash : true, disabled: true, empty: true }), exp);
+    assert.deepStrictEqual(serialize(form, { hash : true, disabled: true, empty: true }), exp);
 };
 
 test('null form', function() {
@@ -426,6 +426,20 @@ test('bracket notation - non-indexed arrays', function() {
     });
 });
 
+test('bracket notation - sparse array', function() {
+    var form = domify('<form>' +
+        '<input name="user[1234]" value="cow" />' +
+        '<input name="user[4567]" value="milk" />' +
+        '</form>');
+
+    hash_check(form, {
+        user: {
+            1234: "cow",
+            4567: "milk",
+        }
+    });
+});
+
 test('bracket notation - nested, non-indexed arrays', function() {
     var form = domify('<form>' +
         '<input name="user[tags][]" value="cow" />' +
@@ -452,19 +466,49 @@ test('bracket notation - indexed arrays', function() {
         '</form>');
 
     hash_check(form, {
-        people: [
-            {
+        people: {
+            0: {
                 name: "fred",
                 age: "12"
             },
-            {
+            1: {
                 name: "bob",
                 age: "14"
             },
-            {
+            2: {
                 name: "bubba",
                 age: "15"
             },
+            3: {
+                age: "2"
+            },
+            _values: [
+                {name: "frank"}
+            ]
+        }
+    });
+});
+
+test('bracket notation - ordered indexed arrays', function() {
+    var form = domify('<form>' +
+        '<input name="people[0][name]" value="fred" />' +
+        '<input name="people[0][age]" value="12" />' +
+        '<input name="people[1][name]" value="bob" />' +
+        '<input name="people[1][age]" value="14" />' +
+        '<input name="people[][name]" value="frank">' +
+        '<input name="people[2][age]" value="2">' +
+        '</form>');
+
+    hash_check(form, {
+        people: [
+            {
+                name: "fred",
+                age: "12"
+            },
+            {
+                name: "bob",
+                age: "14"
+            },
             {
                 name: "frank",
                 age: "2"