diff --git a/src/Illuminate/Support/Collection.php b/src/Illuminate/Support/Collection.php
index 390d068..5aa6156 100644
--- a/src/Illuminate/Support/Collection.php
+++ b/src/Illuminate/Support/Collection.php
@@ -374,8 +374,8 @@ public function keyBy($keyBy)
 
         $results = [];
 
-        foreach ($this->items as $item) {
-            $results[$keyBy($item)] = $item;
+        foreach ($this->items as $key => $item) {
+            $results[$keyBy($item, $key)] = $item;
         }
 
         return new static($results);
@@ -817,7 +817,6 @@ public function sort(callable $callback = null)
         $items = $this->items;
 
         $callback ? uasort($items, $callback) : uasort($items, function ($a, $b) {
-
             if ($a == $b) {
                 return 0;
             }
diff --git a/tests/Support/SupportCollectionTest.php b/tests/Support/SupportCollectionTest.php
index d347b7b..870a817 100644
--- a/tests/Support/SupportCollectionTest.php
+++ b/tests/Support/SupportCollectionTest.php
@@ -23,14 +23,18 @@ public function testLastReturnsLastItemInCollection()
     public function testLastWithCallback()
     {
         $data = new Collection([2, 4, 3, 2]);
-        $result = $data->last(function ($key, $value) { return $value > 2; });
+        $result = $data->last(function ($key, $value) {
+            return $value > 2;
+        });
         $this->assertEquals(3, $result);
     }
 
     public function testLastWithCallbackAndDefault()
     {
         $data = new Collection(['foo', 'bar']);
-        $result = $data->last(function ($key, $value) { return $value === 'baz'; }, 'default');
+        $result = $data->last(function ($key, $value) {
+            return $value === 'baz';
+        }, 'default');
         $this->assertEquals('default', $result);
     }
 
@@ -466,7 +470,9 @@ public function testUniqueWithCallback()
             1 => ['id' => 1, 'first' => 'Taylor', 'last' => 'Otwell'],
             3 => ['id' => 3, 'first' => 'Abigail', 'last' => 'Otwell'],
             5 => ['id' => 5, 'first' => 'Taylor', 'last' => 'Swift'],
-        ], $c->unique(function ($item) { return $item['first'].$item['last']; })->all());
+        ], $c->unique(function ($item) {
+            return $item['first'].$item['last'];
+        })->all());
     }
 
     public function testCollapse()
@@ -509,12 +515,16 @@ public function testSortWithCallback()
     public function testSortBy()
     {
         $data = new Collection(['taylor', 'dayle']);
-        $data = $data->sortBy(function ($x) { return $x; });
+        $data = $data->sortBy(function ($x) {
+            return $x;
+        });
 
         $this->assertEquals(['dayle', 'taylor'], array_values($data->all()));
 
         $data = new Collection(['dayle', 'taylor']);
-        $data = $data->sortByDesc(function ($x) { return $x; });
+        $data = $data->sortByDesc(function ($x) {
+            return $x;
+        });
 
         $this->assertEquals(['taylor', 'dayle'], array_values($data->all()));
     }
@@ -655,8 +665,8 @@ public function testMacroable()
         // Foo() macro : unique values starting with A
         Collection::macro('foo', function () {
             return $this->filter(function ($item) {
-                    return strpos($item, 'a') === 0;
-                })
+                return strpos($item, 'a') === 0;
+            })
                 ->unique()
                 ->values();
         });
@@ -770,7 +780,9 @@ public function testGetPluckValueWithAccessors()
     public function testMap()
     {
         $data = new Collection(['first' => 'taylor', 'last' => 'otwell']);
-        $data = $data->map(function ($item, $key) { return $key.'-'.strrev($item); });
+        $data = $data->map(function ($item, $key) {
+            return $key.'-'.strrev($item);
+        });
         $this->assertEquals(['first' => 'first-rolyat', 'last' => 'last-llewto'], $data->all());
     }
 
@@ -780,28 +792,36 @@ public function testFlatMap()
             ['name' => 'taylor', 'hobbies' => ['programming', 'basketball']],
             ['name' => 'adam', 'hobbies' => ['music', 'powerlifting']],
         ]);
-        $data = $data->flatMap(function ($person) { return $person['hobbies']; });
+        $data = $data->flatMap(function ($person) {
+            return $person['hobbies'];
+        });
         $this->assertEquals(['programming', 'basketball', 'music', 'powerlifting'], $data->all());
     }
 
     public function testTransform()
     {
         $data = new Collection(['first' => 'taylor', 'last' => 'otwell']);
-        $data->transform(function ($item, $key) { return $key.'-'.strrev($item); });
+        $data->transform(function ($item, $key) {
+            return $key.'-'.strrev($item);
+        });
         $this->assertEquals(['first' => 'first-rolyat', 'last' => 'last-llewto'], $data->all());
     }
 
     public function testFirstWithCallback()
     {
         $data = new Collection(['foo', 'bar', 'baz']);
-        $result = $data->first(function ($key, $value) { return $value === 'bar'; });
+        $result = $data->first(function ($key, $value) {
+            return $value === 'bar';
+        });
         $this->assertEquals('bar', $result);
     }
 
     public function testFirstWithCallbackAndDefault()
     {
         $data = new Collection(['foo', 'bar']);
-        $result = $data->first(function ($key, $value) { return $value === 'baz'; }, 'default');
+        $result = $data->first(function ($key, $value) {
+            return $value === 'baz';
+        }, 'default');
         $this->assertEquals('default', $result);
     }
 
@@ -929,7 +949,9 @@ public function testKeyByAttribute()
         $result = $data->keyBy('rating');
         $this->assertEquals([1 => ['rating' => 1, 'name' => '1'], 2 => ['rating' => 2, 'name' => '2'], 3 => ['rating' => 3, 'name' => '3']], $result->all());
 
-        $result = $data->keyBy(function ($item) { return $item['rating'] * 2; });
+        $result = $data->keyBy(function ($item) {
+            return $item['rating'] * 2;
+        });
         $this->assertEquals([2 => ['rating' => 1, 'name' => '1'], 4 => ['rating' => 2, 'name' => '2'], 6 => ['rating' => 3, 'name' => '3']], $result->all());
     }
 
@@ -939,12 +961,12 @@ public function testKeyByClosure()
             ['firstname' => 'Taylor', 'lastname' => 'Otwell', 'locale' => 'US'],
             ['firstname' => 'Lucas', 'lastname' => 'Michot', 'locale' => 'FR'],
         ]);
-        $result = $data->keyBy(function ($item) {
-            return strtolower($item['firstname'].$item['lastname']);
+        $result = $data->keyBy(function ($item, $key) {
+            return strtolower($key.'-'.$item['firstname'].$item['lastname']);
         });
         $this->assertEquals([
-            'taylorotwell' => ['firstname' => 'Taylor', 'lastname' => 'Otwell', 'locale' => 'US'],
-            'lucasmichot'  => ['firstname' => 'Lucas', 'lastname' => 'Michot', 'locale' => 'FR'],
+            '0-taylorotwell' => ['firstname' => 'Taylor', 'lastname' => 'Otwell', 'locale' => 'US'],
+            '1-lucasmichot'  => ['firstname' => 'Lucas', 'lastname' => 'Michot', 'locale' => 'FR'],
         ], $result->all());
     }
 
@@ -954,8 +976,12 @@ public function testContains()
 
         $this->assertTrue($c->contains(1));
         $this->assertFalse($c->contains(2));
-        $this->assertTrue($c->contains(function ($value) { return $value < 5; }));
-        $this->assertFalse($c->contains(function ($value) { return $value > 5; }));
+        $this->assertTrue($c->contains(function ($value) {
+            return $value < 5;
+        }));
+        $this->assertFalse($c->contains(function ($value) {
+            return $value > 5;
+        }));
 
         $c = new Collection([['v' => 1], ['v' => 3], ['v' => 5]]);
 
@@ -975,7 +1001,9 @@ public function testGettingSumFromCollection()
         $this->assertEquals(100, $c->sum('foo'));
 
         $c = new Collection([(object) ['foo' => 50], (object) ['foo' => 50]]);
-        $this->assertEquals(100, $c->sum(function ($i) { return $i->foo; }));
+        $this->assertEquals(100, $c->sum(function ($i) {
+            return $i->foo;
+        }));
     }
 
     public function testCanSumValuesWithoutACallback()
@@ -1027,7 +1055,9 @@ public function testRejectRemovesElementsPassingTruthTest()
         $this->assertEquals(['foo'], $c->reject('bar')->values()->all());
 
         $c = new Collection(['foo', 'bar']);
-        $this->assertEquals(['foo'], $c->reject(function ($v) { return $v == 'bar'; })->values()->all());
+        $this->assertEquals(['foo'], $c->reject(function ($v) {
+            return $v == 'bar';
+        })->values()->all());
 
         $c = new Collection(['foo', null]);
         $this->assertEquals(['foo'], $c->reject(null)->values()->all());
@@ -1036,7 +1066,9 @@ public function testRejectRemovesElementsPassingTruthTest()
         $this->assertEquals(['foo', 'bar'], $c->reject('baz')->values()->all());
 
         $c = new Collection(['foo', 'bar']);
-        $this->assertEquals(['foo', 'bar'], $c->reject(function ($v) { return $v == 'baz'; })->values()->all());
+        $this->assertEquals(['foo', 'bar'], $c->reject(function ($v) {
+            return $v == 'baz';
+        })->values()->all());
 
         $c = new Collection(['id' => 1, 'primary' => 'foo', 'secondary' => 'bar']);
         $this->assertEquals(['primary' => 'foo', 'secondary' => 'bar'], $c->reject(function ($item, $key) {
@@ -1050,8 +1082,12 @@ public function testSearchReturnsIndexOfFirstFoundItem()
 
         $this->assertEquals(1, $c->search(2));
         $this->assertEquals('foo', $c->search('bar'));
-        $this->assertEquals(4, $c->search(function ($value) { return $value > 4; }));
-        $this->assertEquals('foo', $c->search(function ($value) { return ! is_numeric($value); }));
+        $this->assertEquals(4, $c->search(function ($value) {
+            return $value > 4;
+        }));
+        $this->assertEquals('foo', $c->search(function ($value) {
+            return ! is_numeric($value);
+        }));
     }
 
     public function testSearchReturnsFalseWhenItemIsNotFound()
@@ -1060,8 +1096,12 @@ public function testSearchReturnsFalseWhenItemIsNotFound()
 
         $this->assertFalse($c->search(6));
         $this->assertFalse($c->search('foo'));
-        $this->assertFalse($c->search(function ($value) { return $value < 1 && is_numeric($value); }));
-        $this->assertFalse($c->search(function ($value) { return $value == 'nope'; }));
+        $this->assertFalse($c->search(function ($value) {
+            return $value < 1 && is_numeric($value);
+        }));
+        $this->assertFalse($c->search(function ($value) {
+            return $value == 'nope';
+        }));
     }
 
     public function testKeys()
@@ -1220,7 +1260,9 @@ public function testCombineWithCollection()
     public function testReduce()
     {
         $data = new Collection([1, 2, 3]);
-        $this->assertEquals(6, $data->reduce(function ($carry, $element) { return $carry += $element; }));
+        $this->assertEquals(6, $data->reduce(function ($carry, $element) {
+            return $carry += $element;
+        }));
     }
 
     /**