diff --git a/build/controllers/TranslationController.php b/build/controllers/TranslationController.php
index 3ca61667620..550b74975db 100644
--- a/build/controllers/TranslationController.php
+++ b/build/controllers/TranslationController.php
@@ -8,7 +8,6 @@
 namespace yii\build\controllers;
 
 use DirectoryIterator;
-use Yii;
 use yii\console\Controller;
 use yii\helpers\Html;
 
diff --git a/framework/base/ErrorException.php b/framework/base/ErrorException.php
index 8f051a57e1c..f9c388a5453 100644
--- a/framework/base/ErrorException.php
+++ b/framework/base/ErrorException.php
@@ -7,8 +7,6 @@
 
 namespace yii\base;
 
-use Yii;
-
 /**
  * ErrorException represents a PHP error.
  *
diff --git a/framework/base/Security.php b/framework/base/Security.php
index c05084654c0..85faf50e59f 100644
--- a/framework/base/Security.php
+++ b/framework/base/Security.php
@@ -7,7 +7,6 @@
 
 namespace yii\base;
 
-use Yii;
 use yii\helpers\StringHelper;
 
 /**
diff --git a/framework/data/SqlDataProvider.php b/framework/data/SqlDataProvider.php
index 5a8f9631de5..a0fe4bc29a3 100644
--- a/framework/data/SqlDataProvider.php
+++ b/framework/data/SqlDataProvider.php
@@ -7,7 +7,6 @@
 
 namespace yii\data;
 
-use Yii;
 use yii\base\InvalidConfigException;
 use yii\db\Connection;
 use yii\db\Expression;
diff --git a/framework/db/ColumnSchemaBuilder.php b/framework/db/ColumnSchemaBuilder.php
index 756b4b8aa8b..02ca9f2fee9 100644
--- a/framework/db/ColumnSchemaBuilder.php
+++ b/framework/db/ColumnSchemaBuilder.php
@@ -7,7 +7,6 @@
 
 namespace yii\db;
 
-use Yii;
 use yii\base\BaseObject;
 use yii\helpers\StringHelper;
 
diff --git a/framework/i18n/DbMessageSource.php b/framework/i18n/DbMessageSource.php
index 0686291d2a7..e7934be3564 100644
--- a/framework/i18n/DbMessageSource.php
+++ b/framework/i18n/DbMessageSource.php
@@ -7,7 +7,6 @@
 
 namespace yii\i18n;
 
-use Yii;
 use yii\base\InvalidConfigException;
 use yii\caching\CacheInterface;
 use yii\db\Connection;
diff --git a/framework/log/DbTarget.php b/framework/log/DbTarget.php
index 398c49c9fed..d32c292c4f3 100644
--- a/framework/log/DbTarget.php
+++ b/framework/log/DbTarget.php
@@ -7,7 +7,6 @@
 
 namespace yii\log;
 
-use Yii;
 use yii\base\InvalidConfigException;
 use yii\db\Connection;
 use yii\db\Exception;
diff --git a/framework/log/Logger.php b/framework/log/Logger.php
index 6be7eaf2a92..62294c31f93 100644
--- a/framework/log/Logger.php
+++ b/framework/log/Logger.php
@@ -7,7 +7,6 @@
 
 namespace yii\log;
 
-use Yii;
 use yii\base\Component;
 
 /**
diff --git a/framework/log/SyslogTarget.php b/framework/log/SyslogTarget.php
index 8a190d4fb5a..4c22a8b4fe7 100644
--- a/framework/log/SyslogTarget.php
+++ b/framework/log/SyslogTarget.php
@@ -7,7 +7,6 @@
 
 namespace yii\log;
 
-use Yii;
 use yii\helpers\VarDumper;
 
 /**
diff --git a/framework/rbac/Assignment.php b/framework/rbac/Assignment.php
index 21e2ad03bcd..db299813eec 100644
--- a/framework/rbac/Assignment.php
+++ b/framework/rbac/Assignment.php
@@ -7,7 +7,6 @@
 
 namespace yii\rbac;
 
-use Yii;
 use yii\base\BaseObject;
 
 /**
diff --git a/framework/rest/ViewAction.php b/framework/rest/ViewAction.php
index dbe9bb2ac92..901fa6beece 100644
--- a/framework/rest/ViewAction.php
+++ b/framework/rest/ViewAction.php
@@ -7,8 +7,6 @@
 
 namespace yii\rest;
 
-use Yii;
-
 /**
  * ViewAction implements the API endpoint for returning the detailed information about a model.
  *
diff --git a/framework/web/CacheSession.php b/framework/web/CacheSession.php
index 860a91d5803..5763a854096 100644
--- a/framework/web/CacheSession.php
+++ b/framework/web/CacheSession.php
@@ -7,7 +7,6 @@
 
 namespace yii\web;
 
-use Yii;
 use yii\caching\CacheInterface;
 use yii\di\Instance;
 
diff --git a/framework/web/HeaderCollection.php b/framework/web/HeaderCollection.php
index 724e875bc69..17eaadefd6d 100644
--- a/framework/web/HeaderCollection.php
+++ b/framework/web/HeaderCollection.php
@@ -7,7 +7,6 @@
 
 namespace yii\web;
 
-use Yii;
 use yii\base\BaseObject;
 
 /**