diff --git a/lodash.src.js b/lodash.src.js
index f24c2efd8..eb903d24f 100644
--- a/lodash.src.js
+++ b/lodash.src.js
@@ -11309,28 +11309,25 @@
      * @returns {number} Returns the sum.
      * @example
      *
-     * _.sum([4, 6, 2]);
-     * // => 12
+     * _.sum([4, 6]);
+     * // => 10
      *
-     * _.sum({ 'a': 4, 'b': 6, 'c': 2 });
-     * // => 12
+     * _.sum({ 'a': 4, 'b': 6 });
+     * // => 10
      *
-     * _.sum([]);
-     * // => 0
-     *
-     * var users = [
-     *   { 'user': 'barney', 'age': 36 },
-     *   { 'user': 'fred',   'age': 40 }
+     * var objects = [
+     *   { 'n': 4 },
+     *   { 'n': 6 }
      * ];
      *
-     * _.sum(users, function(chr) {
-     *   return chr.age;
+     * _.sum(objects, function(object) {
+     *   return object.n;
      * });
-     * // => 76
+     * // => 10
      *
      * // using the `_.property` callback shorthand
-     * _.sum(users, 'age');
-     * // => 76
+     * _.sum(objects, 'n');
+     * // => 10
      */
     function sum(collection, iteratee, thisArg) {
       if (thisArg && isIterateeCall(collection, iteratee, thisArg)) {
@@ -11339,16 +11336,19 @@
       if (!isArray(collection)) {
         collection = toIterable(collection);
       }
-      var func = getCallback();
-      if (!(func === baseCallback && iteratee == null)) {
+      var func = getCallback(),
+          noIteratee = iteratee == null;
+
+      if (!(func === baseCallback && noIteratee)) {
+        noIteratee = false;
         iteratee = func(iteratee, thisArg, 3);
       }
-
       var length = collection.length,
           result = 0;
 
       while (length--) {
-        result += +(iteratee == null ? collection[length] : iteratee(collection[length])) || 0;
+        var value = collection[length];
+        result += +(noIteratee ? value : iteratee(value)) || 0;
       }
       return result;
     }
diff --git a/test/test.js b/test/test.js
index 11973bf3d..c7d17e81f 100644
--- a/test/test.js
+++ b/test/test.js
@@ -13475,10 +13475,12 @@
   QUnit.module('lodash.sum');
 
   (function() {
-    var objects = [{ 'a': 2 }, { 'a': 3 }, { 'a': 1 }];
+    var array = [6, 4, 2],
+        object = { 'a': 2, 'b': 3, 'c': 1 },
+        objects = [{ 'a': 2 }, { 'a': 3 }, { 'a': 1 }];
 
     test('should return the sum of an array of numbers', 1, function() {
-      strictEqual(_.sum([6, 4, 2]), 12);
+      strictEqual(_.sum(array), 12);
     });
 
     test('should return `0` when passing empty `array` values', 1, function() {
@@ -13496,7 +13498,7 @@
     });
 
     test('should iterate an object', 1, function() {
-      strictEqual(_.sum({ 'a': 1, 'b': 2, 'c': 3 }), 6);
+      strictEqual(_.sum(object), 6);
     });
 
     test('should iterate a string', 2, function() {
@@ -13514,29 +13516,22 @@
     });
 
     test('should support the `thisArg` argument', 1, function() {
-      var actual = _.sum([1, 2.5, 1.5], function(num) {
+      var actual = _.sum([6.8, 4.5, 2.6], function(num) {
         return this.floor(num);
       }, Math);
 
-      strictEqual(actual, 4);
+      strictEqual(actual, 12);
     });
 
     test('should work with a "_.property" style `iteratee`', 2, function() {
-      var actual = _.sum(objects, 'a');
-
-      strictEqual(actual, 6);
-
       var arrays = [[2], [3], [1]];
-      actual = _.sum(arrays, 0);
-
-      strictEqual(actual, 6);
+      strictEqual(_.sum(arrays, 0), 6);
+      strictEqual(_.sum(objects, 'a'), 6);
     });
 
     test('should perform basic sum when used as an iteratee for methods like `_.map`', 1, function() {
-      var array = [{ 'a': 1, 'b': 2, 'c': 3 }, [1, 2, 1]],
-          actual = _.map(array, _.sum);
-
-      deepEqual(actual, [6, 4]);
+      var actual = _.map([array, object], _.sum);
+      deepEqual(actual, [12, 6]);
     });
   }());