diff --git a/AK/FlyString.h b/AK/FlyString.h
index 8f92396928b..d3423522c51 100644
--- a/AK/FlyString.h
+++ b/AK/FlyString.h
@@ -88,6 +88,16 @@ public:
 
     static void did_destroy_impl(Badge<StringImpl>, StringImpl&);
 
+    bool is_one_of() { return false; }
+    template<typename T, typename... Rest>
+    bool is_one_of(const T& string, Rest... rest)
+    {
+        if (string == *this)
+            return true;
+        return is_one_of(rest...);
+    }
+
+
 private:
     RefPtr<StringImpl> m_impl;
 };
diff --git a/AK/String.h b/AK/String.h
index 1f06490696e..e882b8919fc 100644
--- a/AK/String.h
+++ b/AK/String.h
@@ -58,9 +58,9 @@ class String {
 public:
     using ConstIterator = const char*;
 
-    ~String() {}
+    ~String() { }
 
-    String() {}
+    String() { }
     String(const StringView&);
 
     String(const String& other)
@@ -224,6 +224,15 @@ public:
 
     int replace(const String& needle, const String& replacement, bool all_occurences = false);
 
+    bool is_one_of() { return false; }
+    template<typename T, typename... Rest>
+    bool is_one_of(const T& string, Rest... rest)
+    {
+        if (string == *this)
+            return true;
+        return is_one_of(rest...);
+    }
+
 private:
     RefPtr<StringImpl> m_impl;
 };