diff --git a/framework/CHANGELOG.md b/framework/CHANGELOG.md
index 35ee457cc4..c8bac20b8c 100644
--- a/framework/CHANGELOG.md
+++ b/framework/CHANGELOG.md
@@ -31,6 +31,7 @@ Yii Framework 2 Change Log
 - Bug #11723: Fixed PHP 7 + XDebug error handling displaying "Expected array for frame 0" (tanakahisateru)
 - Bug #11735: Fixed `yii\web\UploadedFile` to return `null` when there's no file uploaded (brummm)
 - Bug #11774: Fixed incorrect recusuive symlinks check in FileHelper (AnikanovD)
+- Bug #11739: Fixed `ArrayHelper::index()` losing precision for float keys (AnikanovD)
 
 2.0.8 April 28, 2016
 --------------------
diff --git a/framework/helpers/BaseArrayHelper.php b/framework/helpers/BaseArrayHelper.php
index 480cd139bf..225479372e 100644
--- a/framework/helpers/BaseArrayHelper.php
+++ b/framework/helpers/BaseArrayHelper.php
@@ -363,6 +363,9 @@ class BaseArrayHelper
             } else {
                 $value = static::getValue($element, $key);
                 if ($value !== null) {
+                    if (is_float($value)) {
+                        $value = (string) $value;
+                    }
                     $lastArray[$value] = $element;
                 }
             }
diff --git a/tests/framework/helpers/ArrayHelperTest.php b/tests/framework/helpers/ArrayHelperTest.php
index a524f19094..fde429d124 100644
--- a/tests/framework/helpers/ArrayHelperTest.php
+++ b/tests/framework/helpers/ArrayHelperTest.php
@@ -424,6 +424,30 @@ class ArrayHelperTest extends TestCase
         $this->assertEquals($expected, $result);
     }
 
+    /**
+     * @see https://github.com/yiisoft/yii2/issues/11739
+     */
+    public function testIndexFloat()
+    {
+        $array = [
+            ['id' => 1e6],
+            ['id' => 1e32],
+            ['id' => 1e64],
+            ['id' => 1465540807.522109],
+        ];
+
+        $expected = [
+            '1000000' => ['id' => 1e6],
+            '1.0E+32' => ['id' => 1e32],
+            '1.0E+64' => ['id' => 1e64],
+            '1465540807.5221' => ['id' => 1465540807.522109],
+        ];
+
+        $result = ArrayHelper::index($array, 'id');
+
+        $this->assertEquals($expected, $result);
+    }
+
     public function testGetColumn()
     {
         $array = [