diff --git a/src/Illuminate/Support/Collection.php b/src/Illuminate/Support/Collection.php
index bd19409e1d10..ac8f991a9e3c 100644
--- a/src/Illuminate/Support/Collection.php
+++ b/src/Illuminate/Support/Collection.php
@@ -1899,14 +1899,14 @@ public function count()
     public function countBy($predicate = null)
     {
         if (is_null($predicate)) {
-            $predicate = function ($val, $key) {
+            $predicate = function ($val) {
                 return $val;
             };
         }
 
         return new static(
             $this->groupBy($predicate)
-                ->map(function ($val, $key) {
+                ->map(function ($val) {
                     return $val->count();
                 })
         );
diff --git a/tests/Support/SupportCollectionTest.php b/tests/Support/SupportCollectionTest.php
index 0b21f1d0efa0..2b47481fa681 100755
--- a/tests/Support/SupportCollectionTest.php
+++ b/tests/Support/SupportCollectionTest.php
@@ -309,25 +309,25 @@ public function testCountable()
 
     public function testCountableByWithoutPredicate()
     {
-        $c = new Collection([ 'foo', 'foo', 'foo', 'bar', 'bar', 'foobar' ]);
-        $this->assertEquals([ 'foo' => 3, 'bar' => 2, 'foobar' => 1 ], $c->countBy()->all());
+        $c = new Collection(['foo', 'foo', 'foo', 'bar', 'bar', 'foobar']);
+        $this->assertEquals(['foo' => 3, 'bar' => 2, 'foobar' => 1], $c->countBy()->all());
 
-        $c = new Collection([ true, true, false, false, false ]);
-        $this->assertEquals([ true => 2, false => 3, ], $c->countBy()->all());
+        $c = new Collection([true, true, false, false, false]);
+        $this->assertEquals([true => 2, false => 3,], $c->countBy()->all());
 
-        $c = new Collection([ 1, 5, 1, 5, 5, 1 ]);
-        $this->assertEquals([ 1 => 3, 5 => 3, ], $c->countBy()->all());
+        $c = new Collection([1, 5, 1, 5, 5, 1]);
+        $this->assertEquals([1 => 3, 5 => 3,], $c->countBy()->all());
     }
 
     public function testCountableByWithPredicate()
     {
-        $c = new Collection([ 'alice', 'aaron', 'bob', 'carla' ]);
-        $this->assertEquals([ 'a' => 2, 'b' => 1, 'c' => 1 ], $c->countBy(function ($name) {
+        $c = new Collection(['alice', 'aaron', 'bob', 'carla']);
+        $this->assertEquals(['a' => 2, 'b' => 1, 'c' => 1], $c->countBy(function ($name) {
             return substr($name, 0, 1);
         })->all());
 
-        $c = new Collection([ 1, 2, 3, 4, 5 ]);
-        $this->assertEquals([ true => 2, false => 3 ], $c->countBy(function ($i) {
+        $c = new Collection([1, 2, 3, 4, 5]);
+        $this->assertEquals([true => 2, false => 3], $c->countBy(function ($i) {
             return $i % 2 === 0;
         })->all());
     }