diff --git a/src/Twig/Runtime/IconRuntime.php b/src/Twig/Runtime/IconRuntime.php
index 1179415..10ba367 100644
--- a/src/Twig/Runtime/IconRuntime.php
+++ b/src/Twig/Runtime/IconRuntime.php
@@ -10,19 +10,16 @@ use Twig\Extension\RuntimeExtensionInterface;
 
 final class IconRuntime implements RuntimeExtensionInterface
 {
-    public const DEFAULT_SIZE = 32;
-    public const DEFAULT_COLOUR = 'primary';
-
-    private const DEFAULT_OPTIONS = [
+    private const OPTIONS = [
         'icon'    => null,
         'title'   => null,
-        'size'    => self::DEFAULT_SIZE,
-        'colour'  => self::DEFAULT_COLOUR,
+        'size'    => null,
+        'colour'  => null,
         'hover'   => null,
         'classes' => [],
     ];
 
-    public function __construct(private array $directories, private array $colours)
+    public function __construct(private array $defaultOptions, private array $directories, private array $colours)
     {}
 
     /**
@@ -76,13 +73,17 @@ final class IconRuntime implements RuntimeExtensionInterface
 
     private function mergeUserOptionsWithDefaults(array $userOptions): array
     {
-        return array_merge(self::DEFAULT_OPTIONS, $userOptions);
+        $options = self::OPTIONS;
+        $options['size'] = $this->defaultOptions['size'];
+        $options['colour'] = $this->defaultOptions['colour'];
+
+        return array_merge($options, $userOptions);
     }
 
     private function throwIfUnrecognisedOptionExists(array $options): void
     {
         foreach (array_keys($options) as $key) {
-            if (!key_exists($key, self::DEFAULT_OPTIONS)) {
+            if (!key_exists($key, self::OPTIONS)) {
                 throw new \InvalidArgumentException("Unrecognised option '{$key}'!");
             }
         }