diff --git a/src/PcmIconBundle.php b/src/PcmIconBundle.php
index 17eb2ce..ff510f5 100644
--- a/src/PcmIconBundle.php
+++ b/src/PcmIconBundle.php
@@ -5,10 +5,7 @@ declare(strict_types=1);
 namespace Pcm\IconBundle;
 
 use Pcm\IconBundle\DependencyInjection\PcmIconExtension;
-use Symfony\Component\Config\Definition\Configurator\DefinitionConfigurator;
-use Symfony\Component\DependencyInjection\ContainerBuilder;
 use Symfony\Component\DependencyInjection\Extension\ExtensionInterface;
-use Symfony\Component\DependencyInjection\Loader\Configurator\ContainerConfigurator;
 use Symfony\Component\HttpKernel\Bundle\AbstractBundle;
 
 class PcmIconBundle extends AbstractBundle
diff --git a/src/Twig/Extension/IconExtension.php b/src/Twig/Extension/IconExtension.php
new file mode 100644
index 0000000..1732b96
--- /dev/null
+++ b/src/Twig/Extension/IconExtension.php
@@ -0,0 +1,22 @@
+<?php
+
+declare(strict_types=1);
+
+namespace Pcm\IconBundle\Twig\Extension;
+
+use Pcm\IconBundle\Twig\Runtime\IconRuntime;
+use Twig\Extension\AbstractExtension;
+use Twig\TwigFunction;
+
+final class IconExtension extends AbstractExtension
+{
+    /**
+     * @inheritDoc
+     */
+    public function getFunctions(): array
+    {
+        return [
+            new TwigFunction('icon', [IconRuntime::class, 'renderIcon'])
+        ];
+    }
+}
diff --git a/src/Twig/Functions/IconExtension.php b/src/Twig/Runtime/IconRuntime.php
similarity index 93%
rename from src/Twig/Functions/IconExtension.php
rename to src/Twig/Runtime/IconRuntime.php
index 2fa3742..d3006e8 100644
--- a/src/Twig/Functions/IconExtension.php
+++ b/src/Twig/Runtime/IconRuntime.php
@@ -2,12 +2,13 @@
 
 declare(strict_types=1);
 
-namespace Pcm\IconBundle\Twig\Functions;
+namespace Pcm\IconBundle\Twig\Runtime;
 
-use Twig\Extension\AbstractExtension;
-use Twig\TwigFunction;
+use Pcm\IconBundle\Exception\ColourNotFound;
+use Pcm\IconBundle\Exception\IconNotFound;
+use Twig\Extension\RuntimeExtensionInterface;
 
-final class IconExtension extends AbstractExtension
+final class IconRuntime implements RuntimeExtensionInterface
 {
     public const DEFAULT_SIZE = 32;
 
@@ -22,18 +23,6 @@ final class IconExtension extends AbstractExtension
 
     public function __construct(private array $directories, private array $colours) {}
 
-    /**
-     * @inheritDoc
-     */
-    public function getFunctions(): array
-    {
-        return [
-            new TwigFunction('icon', [$this, 'renderIcon'], [
-                'is_safe' => ['html']
-            ])
-        ];
-    }
-
     /**
      * @param array $options
      * ```
@@ -211,7 +200,3 @@ final class IconExtension extends AbstractExtension
         }
     }
 }
-
-class IconNotFound extends \Exception {};
-
-class ColourNotFound extends \Exception {};
diff --git a/tests/Twig/Functions/IconExtensionTest.php b/tests/Twig/Runtime/IconRuntimeTest.php
similarity index 95%
rename from tests/Twig/Functions/IconExtensionTest.php
rename to tests/Twig/Runtime/IconRuntimeTest.php
index 337b1a0..f8ca7c6 100644
--- a/tests/Twig/Functions/IconExtensionTest.php
+++ b/tests/Twig/Runtime/IconRuntimeTest.php
@@ -4,12 +4,12 @@ declare(strict_types=1);
 
 namespace Pcm\IconBundle\Tests\Twig\Functions;
 
-use Pcm\IconBundle\Twig\Functions\IconExtension;
-use Pcm\IconBundle\Twig\Functions\IconNotFound;
-use Pcm\IconBundle\Twig\Functions\ColourNotFound;
+use Pcm\IconBundle\Exception\ColourNotFound;
+use Pcm\IconBundle\Exception\IconNotFound;
+use Pcm\IconBundle\Twig\Runtime\IconRuntime;
 use PHPUnit\Framework\TestCase;
 
-class IconExtensionTest extends TestCase
+class IconRuntimeTest extends TestCase
 {
     private const ICON = 'test';
 
@@ -32,11 +32,14 @@ class IconExtensionTest extends TestCase
         ]
     ];
 
-    private IconExtension $icon;
+    private IconRuntime $icon;
 
     protected function setUp(): void
     {
-        $this->icon = new IconExtension(['tests/icons'], self::COLOURS);
+        $this->icon = new IconRuntime(
+            directories: ['tests/icons'],
+            colours: self::COLOURS
+        );
     }
 
     public function testThrowsWhenPassedAnInvalidIconName(): void
@@ -119,7 +122,7 @@ class IconExtensionTest extends TestCase
 
     public function testDefaultSizeIsSetOnSvgIfNoSizeOptionPassed(): void
     {
-        $defaultSize = IconExtension::DEFAULT_SIZE;
+        $defaultSize = IconRuntime::DEFAULT_SIZE;
         $content = $this->icon->renderIcon(['icon' => self::ICON]);
 
         $regex = "/^<svg.+?width=\"{$defaultSize}\"/";
@@ -131,7 +134,7 @@ class IconExtensionTest extends TestCase
 
     public function testDefaultSizeIsOnlySetOnce(): void
     {
-        $defaultSize = IconExtension::DEFAULT_SIZE;
+        $defaultSize = IconRuntime::DEFAULT_SIZE;
         $content = $this->icon->renderIcon(['icon' => self::ICON]);
 
         $widthRegex = "/width=\"{$defaultSize}\"/";