diff --git a/Userland/Libraries/LibWeb/CSS/CSSImportRule.h b/Userland/Libraries/LibWeb/CSS/CSSImportRule.h
index 2c752daab7..e097f80888 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSImportRule.h
+++ b/Userland/Libraries/LibWeb/CSS/CSSImportRule.h
@@ -60,4 +60,7 @@ private:
     RefPtr<CSSStyleSheet> m_style_sheet;
 };
 
+template<>
+inline bool CSSRule::fast_is<CSSImportRule>() const { return type() == CSSRule::Type::Import; }
+
 }
diff --git a/Userland/Libraries/LibWeb/CSS/CSSRule.h b/Userland/Libraries/LibWeb/CSS/CSSRule.h
index 63fa5c1868..d7f3b51eeb 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSRule.h
+++ b/Userland/Libraries/LibWeb/CSS/CSSRule.h
@@ -47,6 +47,9 @@ public:
     virtual StringView class_name() const = 0;
     virtual Type type() const = 0;
 
+    template<typename T>
+    bool fast_is() const = delete;
+
 private:
 };
 
diff --git a/Userland/Libraries/LibWeb/CSS/CSSStyleRule.h b/Userland/Libraries/LibWeb/CSS/CSSStyleRule.h
index e8db816f6c..abee9ce941 100644
--- a/Userland/Libraries/LibWeb/CSS/CSSStyleRule.h
+++ b/Userland/Libraries/LibWeb/CSS/CSSStyleRule.h
@@ -59,4 +59,7 @@ private:
     NonnullRefPtr<CSSStyleDeclaration> m_declaration;
 };
 
+template<>
+inline bool CSSRule::fast_is<CSSStyleRule>() const { return type() == CSSRule::Type::Style; }
+
 }