diff --git a/src/Standards/Typo3Update/Sniffs/Removed/ExtensionKeySniff.php b/src/Standards/Typo3Update/Sniffs/Removed/ExtensionKeySniff.php
new file mode 100644
index 0000000..ef93ceb
--- /dev/null
+++ b/src/Standards/Typo3Update/Sniffs/Removed/ExtensionKeySniff.php
@@ -0,0 +1,58 @@
+<?php
+
+/**
+ * Created by PhpStorm.
+ * User: dah
+ * Date: 11.04.17
+ * Time: 12:12
+ */
+class Typo3Update_Sniffs_Removed_ExtensionKeySniff extends \Typo3Update\Sniffs\Removed\AbstractGenericUsage
+{
+    /**
+     * Return file names containing removed configurations.
+     *
+     * @return array<string>
+     */
+    protected function getRemovedConfigFiles()
+    {
+        return [];
+    }
+
+    /**
+     * The original call, to allow user to check matches.
+     *
+     * As we match the name, that can be provided by multiple classes, you
+     * should provide an example, so users can check that this is the legacy
+     * one.
+     *
+     * @param array $config
+     *
+     * @return string
+     */
+    protected function getOldUsage(array $config)
+    {
+        return '';
+    }
+
+    /**
+     * Registers the tokens that this sniff wants to listen for.
+     *
+     * An example return value for a sniff that wants to listen for whitespace
+     * and any comments would be:
+     *
+     * <code>
+     *    return array(
+     *            T_WHITESPACE,
+     *            T_DOC_COMMENT,
+     *            T_COMMENT,
+     *           );
+     * </code>
+     *
+     * @return int[]
+     * @see    Tokens.php
+     */
+    public function register()
+    {
+        return [];
+    }
+}
diff --git a/tests/Fixtures/Standards/Typo3Update/Sniffs/Removed/ExtensionKeySniff/Expected.json b/tests/Fixtures/Standards/Typo3Update/Sniffs/Removed/ExtensionKeySniff/Expected.json
new file mode 100644
index 0000000..22c013b
--- /dev/null
+++ b/tests/Fixtures/Standards/Typo3Update/Sniffs/Removed/ExtensionKeySniff/Expected.json
@@ -0,0 +1,24 @@
+{
+    "files": {
+        "InputFileForIssues.php": {
+            "errors": 0,
+            "messages": [
+                {
+                    "column": 63,
+                    "fixable": false,
+                    "line": 22,
+                    "message": "Legacy extension are not allowed; found \"perm\"",
+                    "severity": 5,
+                    "source": "Typo3Update.Removed.ExtensionKey.legacyKey",
+                    "type": "WARNING"
+                }
+            ],
+            "warnings": 1
+        }
+    },
+    "totals": {
+        "errors": 0,
+        "fixable": 0,
+        "warnings": 1
+    }
+}
diff --git a/tests/Fixtures/Standards/Typo3Update/Sniffs/Removed/ExtensionKeySniff/InputFileForIssues.php b/tests/Fixtures/Standards/Typo3Update/Sniffs/Removed/ExtensionKeySniff/InputFileForIssues.php
new file mode 100644
index 0000000..2cf7985
--- /dev/null
+++ b/tests/Fixtures/Standards/Typo3Update/Sniffs/Removed/ExtensionKeySniff/InputFileForIssues.php
@@ -0,0 +1,22 @@
+<?php
+
+/*
+ * Copyright (C) 2017  Daniel Siepmann <coding@daniel-siepmann.de>
+ *
+ * This program is free software; you can redistribute it and/or
+ * modify it under the terms of the GNU General Public License
+ * as published by the Free Software Foundation; either version 2
+ * of the License, or (at your option) any later version.
+ *
+ * This program is distributed in the hope that it will be useful,
+ * but WITHOUT ANY WARRANTY; without even the implied warranty of
+ * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
+ * GNU General Public License for more details.
+ *
+ * You should have received a copy of the GNU General Public License
+ * along with this program; if not, write to the Free Software
+ * Foundation, Inc., 51 Franklin Street, Fifth Floor, Boston, MA
+ * 02110-1301, USA.
+ */
+
+\TYPO3\CMS\Core\Utility\ExtensionManagementUtility::isLoaded('perm');