diff --git a/src/Environment.php b/src/Environment.php
index 003a44816..d26b368e0 100644
--- a/src/Environment.php
+++ b/src/Environment.php
@@ -374,8 +374,7 @@ class Environment
             }
         }
 
-        // to be removed in 3.0
-        $this->extensionSet->initRuntime($this);
+        $this->extensionSet->initRuntime();
 
         return $this->loadedTemplates[$cls] = new $cls($this);
     }
diff --git a/src/Extension/InitRuntimeInterface.php b/src/Extension/InitRuntimeInterface.php
deleted file mode 100644
index 076bdbb98..000000000
--- a/src/Extension/InitRuntimeInterface.php
+++ /dev/null
@@ -1,34 +0,0 @@
-<?php
-
-/*
- * This file is part of Twig.
- *
- * (c) Fabien Potencier
- *
- * For the full copyright and license information, please view the LICENSE
- * file that was distributed with this source code.
- */
-
-namespace Twig\Extension;
-
-use Twig\Environment;
-
-/**
- * Enables usage of the deprecated Twig\Extension\AbstractExtension::initRuntime() method.
- *
- * Explicitly implement this interface if you really need to implement the
- * deprecated initRuntime() method in your extensions.
- *
- * @author Fabien Potencier <fabien@symfony.com>
- *
- * @deprecated since Twig 2.7, to be removed in 3.0
- */
-interface InitRuntimeInterface
-{
-    /**
-     * Initializes the runtime environment.
-     *
-     * This is where you can load some file that contains filter functions for instance.
-     */
-    public function initRuntime(Environment $environment);
-}
diff --git a/src/ExtensionSet.php b/src/ExtensionSet.php
index d09ed793c..6e32a0f76 100644
--- a/src/ExtensionSet.php
+++ b/src/ExtensionSet.php
@@ -14,7 +14,6 @@ namespace Twig;
 use Twig\Error\RuntimeError;
 use Twig\Extension\ExtensionInterface;
 use Twig\Extension\GlobalsInterface;
-use Twig\Extension\InitRuntimeInterface;
 use Twig\Extension\StagingExtension;
 use Twig\NodeVisitor\NodeVisitorInterface;
 use Twig\TokenParser\TokenParserInterface;
@@ -47,24 +46,9 @@ final class ExtensionSet
         $this->staging = new StagingExtension();
     }
 
-    /**
-     * Initializes the runtime environment.
-     *
-     * @deprecated since Twig 2.7
-     */
-    public function initRuntime(Environment $env)
+    public function initRuntime()
     {
-        if ($this->runtimeInitialized) {
-            return;
-        }
-
         $this->runtimeInitialized = true;
-
-        foreach ($this->extensions as $extension) {
-            if ($extension instanceof InitRuntimeInterface) {
-                $extension->initRuntime($env);
-            }
-        }
     }
 
     public function hasExtension(string $class): bool
diff --git a/test/Twig/Tests/EnvironmentTest.php b/test/Twig/Tests/EnvironmentTest.php
index ad7ef591e..972757e7e 100644
--- a/test/Twig/Tests/EnvironmentTest.php
+++ b/test/Twig/Tests/EnvironmentTest.php
@@ -15,7 +15,6 @@ use Twig\Environment;
 use Twig\Extension\AbstractExtension;
 use Twig\Extension\ExtensionInterface;
 use Twig\Extension\GlobalsInterface;
-use Twig\Extension\InitRuntimeInterface;
 use Twig\Loader\ArrayLoader;
 use Twig\Loader\LoaderInterface;
 use Twig\Node\Node;
@@ -305,22 +304,6 @@ class Twig_Tests_EnvironmentTest extends \PHPUnit\Framework\TestCase
         $this->assertTrue($twig->isTemplateFresh('page', time()));
     }
 
-    /**
-     * @group legacy
-     */
-    public function testInitRuntimeWithAnExtensionUsingInitRuntimeNoDeprecation()
-    {
-        $loader = $this->getMockBuilder(LoaderInterface::class)->getMock();
-        $twig = new Environment($loader);
-        $loader->expects($this->once())->method('getSourceContext')->will($this->returnValue(new Source('', '')));
-        $twig->addExtension(new Twig_Tests_EnvironmentTest_ExtensionWithoutDeprecationInitRuntime());
-        $twig->load('');
-
-        // add a dummy assertion here to satisfy PHPUnit, the only thing we want to test is that the code above
-        // can be executed without throwing any deprecations
-        $this->addToAssertionCount(1);
-    }
-
     /**
      * @expectedException \LogicException
      * @expectedExceptionMessage Unable to register extension "Twig_Tests_EnvironmentTest_Extension" as it is already registered.
@@ -479,20 +462,6 @@ class Twig_Tests_EnvironmentTest_NodeVisitor implements NodeVisitorInterface
     }
 }
 
-class Twig_Tests_EnvironmentTest_ExtensionWithDeprecationInitRuntime extends AbstractExtension
-{
-    public function initRuntime(Environment $env)
-    {
-    }
-}
-
-class Twig_Tests_EnvironmentTest_ExtensionWithoutDeprecationInitRuntime extends AbstractExtension implements InitRuntimeInterface
-{
-    public function initRuntime(Environment $env)
-    {
-    }
-}
-
 class Twig_Tests_EnvironmentTest_ExtensionWithoutRuntime extends AbstractExtension
 {
     public function getFunctions()