diff --git a/CHANGELOG.md b/CHANGELOG.md
index 76b62e0..5bfd428 100644
--- a/CHANGELOG.md
+++ b/CHANGELOG.md
@@ -4,6 +4,10 @@ All Notable changes to `commonmark-extras` will be documented in this file
 
 ## [Unreleased][unreleased]
 
+### Added
+
+ - Added support for [league/commonmark-ext-strikethrough v0.4.0](https://github.com/thephpleague/commonmark-ext-strikethrough/releases/tag/v0.4.0)
+
 ## [0.3.0] - 2019-04-10
 
 ### Changed
diff --git a/README.md b/README.md
index 91d8dfb..b27b775 100644
--- a/README.md
+++ b/README.md
@@ -16,6 +16,7 @@ Adding this extension to your project will automatically register these sub-exte
 | :------------ | :---------- |
 | [league/commonmark-ext-autolink](https://github.com/thephpleague/commonmark-ext-autolink) | Automatically creating links to URLs and email address (without needing the `<...>` syntax) |
 | [league/commonmark-ext-smartpunct](https://github.com/thephpleague/commonmark-ext-smartpunct) | Intelligently converts ASCII quotes, dashes, and ellipses to their Unicode equivalents |
+| [league/commonmark-ext-strikethrough](https://github.com/thephpleague/commonmark-ext-strikethrough) | Adds support for `~~strikethrough~~` syntax |
 
 ## Install
 
diff --git a/composer.json b/composer.json
index d011941..3dd9d73 100644
--- a/composer.json
+++ b/composer.json
@@ -17,6 +17,7 @@
         "php" : "^7.1",
         "league/commonmark": "^0.19.1",
         "league/commonmark-ext-smartpunct": "^0.2",
+        "league/commonmark-ext-strikethrough": "^0.4",
         "league/commonmark-ext-autolink": "^0.3"
     },
     "require-dev": {
diff --git a/src/CommonMarkExtrasExtension.php b/src/CommonMarkExtrasExtension.php
index 37fd2f3..c39e92f 100644
--- a/src/CommonMarkExtrasExtension.php
+++ b/src/CommonMarkExtrasExtension.php
@@ -14,6 +14,7 @@
 use League\CommonMark\ConfigurableEnvironmentInterface;
 use League\CommonMark\Ext\Autolink\AutolinkExtension;
 use League\CommonMark\Ext\SmartPunct\SmartPunctExtension;
+use League\CommonMark\Ext\Strikethrough\StrikethroughExtension;
 use League\CommonMark\Extension\ExtensionInterface;
 
 final class CommonMarkExtrasExtension implements ExtensionInterface
@@ -21,6 +22,7 @@ final class CommonMarkExtrasExtension implements ExtensionInterface
     public function register(ConfigurableEnvironmentInterface $environment)
     {
         $environment->addExtension(new SmartPunctExtension());
+        $environment->addExtension(new StrikethroughExtension());
         $environment->addExtension(new AutolinkExtension());
     }
 }
diff --git a/tests/CommonMarkExtrasExtensionTest.php b/tests/CommonMarkExtrasExtensionTest.php
index f4dfcd5..d838afa 100644
--- a/tests/CommonMarkExtrasExtensionTest.php
+++ b/tests/CommonMarkExtrasExtensionTest.php
@@ -21,11 +21,11 @@ final class CommonMarkExtrasExtensionTest extends TestCase
     public function testExtension()
     {
         $input = <<<EOT
-"You can contact the author of this library at colinodell@gmail.com or check out his website: https://www.colinodell.com"
+"You can contact the author of this ~~project~~ library at colinodell@gmail.com or check out his website: https://www.colinodell.com"
 EOT;
 
         $expected = <<<EOT
-<p>“You can contact the author of this library at <a href="mailto:colinodell@gmail.com">colinodell@gmail.com</a> or check out his website: <a href="https://www.colinodell.com">https://www.colinodell.com</a>”</p>
+<p>“You can contact the author of this <del>project</del> library at <a href="mailto:colinodell@gmail.com">colinodell@gmail.com</a> or check out his website: <a href="https://www.colinodell.com">https://www.colinodell.com</a>”</p>
 
 EOT;