diff --git a/src/Twig/Functions/IconExtension.php b/src/Twig/Functions/IconExtension.php
index 4fc6ee4..a7ca8a5 100644
--- a/src/Twig/Functions/IconExtension.php
+++ b/src/Twig/Functions/IconExtension.php
@@ -77,10 +77,14 @@ final class IconExtension extends AbstractExtension
         $rawSvgMarkup = $this->getSvgMarkup($iconFilepath);
         $cleanSvgMarkup = $this->cleanSvgMarkup($rawSvgMarkup);
 
-        $mainColour = $this->getMainPallete($options['colour']);
+        $mainPallete = $this->getMainPallete($options['colour']);
+
+        $xml = new \SimpleXMLElement($cleanSvgMarkup);
+        $xml = $this->addAttributeToXmlElement($xml, 'class', $mainPallete['stroke'] . ' ' . $mainPallete['fill']);
+        $markup = $this->removeXMLDeclaration($xml->saveXML());
 
         if ($this->isNonEmptyString($options['title']))
-            $markup = $this->addTitleToMarkup($cleanSvgMarkup, $options['title']);
+            $markup = $this->addTitleToMarkup($markup, $options['title']);
 
         if ($options['size'] < 0)
             throw new \InvalidArgumentException('Size must not be negative');
@@ -175,12 +179,12 @@ final class IconExtension extends AbstractExtension
 
     private function removeBlackStrokeAttributes(string $content): string
     {
-        return preg_replace('/stroke="\s*(#0{6}|#000)|(rgb\(\s*0,\s*0,\s*0\s*\))|(black)\s*"/', '', $content);
+        return preg_replace('/stroke="\s*(#0{6}|#000|rgb\(\s*0,\s*0,\s*0\s*\)|black)\s*"/', '', $content);
     }
 
     private function removeBlackFillAttributes(string $content): string
     {
-        return preg_replace('/fill="\s*(#0{6}|#000)|(rgb\(\s*0,\s*0,\s*0\s*\))|(black)\s*"/', '', $content);
+        return preg_replace('/fill="\s*(#0{6}|#000|rgb\(\s*0,\s*0,\s*0\s*\)|black)\s*"/', '', $content);
     }
 }
 
diff --git a/tests/Twig/Functions/IconExtensionTest.php b/tests/Twig/Functions/IconExtensionTest.php
index 78716af..7dcf618 100644
--- a/tests/Twig/Functions/IconExtensionTest.php
+++ b/tests/Twig/Functions/IconExtensionTest.php
@@ -17,6 +17,10 @@ class IconExtensionTest extends TestCase
         'primary' => [
             'stroke' => 'stroke-primary',
             'fill' => 'fill-primary'
+        ],
+        'white' => [
+            'stroke' => 'stroke-white',
+            'fill' => 'fill-white'
         ]
     ];
 
@@ -211,4 +215,12 @@ class IconExtensionTest extends TestCase
         $this->icon->renderIcon(['icon' => self::ICON, 'colour' => 'red']);
     }
 
+    public function testSvgClassContainsPalleteClasses(): void
+    {
+        $contents = $this->icon->renderIcon(['icon' => self::ICON, 'colour' => 'white']);
+        $this->assertMatchesRegularExpression('/<svg.*?class=".*?fill-white.*?>/', $contents);
+        $this->assertMatchesRegularExpression('/<svg.*?class=".*?stroke-white?.*>/', $contents);
+    }
+
+
 }