diff --git a/lib/utils.js b/lib/utils.js
index ebe8867e..f778daae 100644
--- a/lib/utils.js
+++ b/lib/utils.js
@@ -12,7 +12,7 @@ var hexTable = (function () {
 var has = Object.prototype.hasOwnProperty;
 
 exports.arrayToObject = function (source, options) {
-    var obj = options.plainObjects ? Object.create(null) : {};
+    var obj = options && options.plainObjects ? Object.create(null) : {};
     for (var i = 0; i < source.length; ++i) {
         if (typeof source[i] !== 'undefined') {
             obj[i] = source[i];
@@ -22,16 +22,30 @@ exports.arrayToObject = function (source, options) {
     return obj;
 };
 
-exports.merge = function (target, source, options) {
+var isArray = Array.isArray;
+
+var arrayToObject = function arrayToObject(source, options) {
+    var obj = options && options.plainObjects ? Object.create(null) : {};
+    for (var i = 0; i < source.length; ++i) {
+        if (typeof source[i] !== 'undefined') {
+            obj[i] = source[i];
+        }
+    }
+
+    return obj;
+};
+
+exports.merge = function merge(target, source, options) {
+    /* eslint no-param-reassign: 0 */
     if (!source) {
         return target;
     }
 
     if (typeof source !== 'object') {
-        if (Array.isArray(target)) {
+        if (isArray(target)) {
             target.push(source);
-        } else if (typeof target === 'object') {
-            if (options.plainObjects || options.allowPrototypes || !has.call(Object.prototype, source)) {
+        } else if (target && typeof target === 'object') {
+            if ((options && (options.plainObjects || options.allowPrototypes)) || !has.call(Object.prototype, source)) {
                 target[source] = true;
             }
         } else {
@@ -41,20 +55,36 @@ exports.merge = function (target, source, options) {
         return target;
     }
 
-    if (typeof target !== 'object') {
+    if (!target || typeof target !== 'object') {
         return [target].concat(source);
     }
 
     var mergeTarget = target;
-    if (Array.isArray(target) && !Array.isArray(source)) {
-        mergeTarget = exports.arrayToObject(target, options);
+    if (isArray(target) && !isArray(source)) {
+        mergeTarget = arrayToObject(target, options);
+    }
+
+    if (isArray(target) && isArray(source)) {
+        source.forEach(function (item, i) {
+            if (has.call(target, i)) {
+                var targetItem = target[i];
+                if (targetItem && typeof targetItem === 'object' && item && typeof item === 'object') {
+                    target[i] = merge(targetItem, item, options);
+                } else {
+                    target.push(item);
+                }
+            } else {
+                target[i] = item;
+            }
+        });
+        return target;
     }
 
     return Object.keys(source).reduce(function (acc, key) {
         var value = source[key];
 
         if (has.call(acc, key)) {
-            acc[key] = exports.merge(acc[key], value, options);
+            acc[key] = merge(acc[key], value, options);
         } else {
             acc[key] = value;
         }
@@ -132,7 +162,7 @@ exports.compact = function (obj, references) {
 
     refs.push(obj);
 
-    if (Array.isArray(obj)) {
+    if (isArray(obj)) {
         var compacted = [];
 
         for (var i = 0; i < obj.length; ++i) {
diff --git a/test/utils.js b/test/utils.js
index 4a8d8246..999f860d 100644
--- a/test/utils.js
+++ b/test/utils.js
@@ -5,5 +5,21 @@ var utils = require('../lib/utils');
 
 test('merge()', function (t) {
     t.deepEqual(utils.merge({ a: 'b' }, { a: 'c' }), { a: ['b', 'c'] }, 'merges two objects with the same key');
+
+    var oneMerged = utils.merge({ foo: 'bar' }, { foo: { first: '123' } });
+    t.deepEqual(oneMerged, { foo: ['bar', { first: '123' }] }, 'merges a standalone and an object into an array');
+
+    var twoMerged = utils.merge({ foo: ['bar', { first: '123' }] }, { foo: { second: '456' } });
+    t.deepEqual(twoMerged, { foo: { 0: 'bar', 1: { first: '123' }, second: '456' } }, 'merges a standalone and two objects into an array');
+
+    var sandwiched = utils.merge({ foo: ['bar', { first: '123', second: '456' }] }, { foo: 'baz' });
+    t.deepEqual(sandwiched, { foo: ['bar', { first: '123', second: '456' }, 'baz'] }, 'merges an object sandwiched by two standalones into an array');
+
+    var nestedArrays = utils.merge({ foo: ['baz'] }, { foo: ['bar', 'xyzzy'] });
+    t.deepEqual(nestedArrays, { foo: ['baz', 'bar', 'xyzzy'] });
+
+    var noOptionsNonObjectSource = utils.merge({ foo: 'baz' }, 'bar');
+    t.deepEqual(noOptionsNonObjectSource, { foo: 'baz', bar: true });
+
     t.end();
 });