diff --git a/Libraries/LibJS/Runtime/BoundFunction.h b/Libraries/LibJS/Runtime/BoundFunction.h
index b22673cb0c..1e8b3e46b3 100644
--- a/Libraries/LibJS/Runtime/BoundFunction.h
+++ b/Libraries/LibJS/Runtime/BoundFunction.h
@@ -36,9 +36,14 @@ private:
     ThrowCompletionOr<void> get_stack_frame_size(size_t& registers_and_constants_and_locals_count, size_t& argument_count) override;
     virtual void visit_edges(Visitor&) override;
 
+    virtual bool is_bound_function() const final { return true; }
+
     GC::Ptr<FunctionObject> m_bound_target_function; // [[BoundTargetFunction]]
     Value m_bound_this;                              // [[BoundThis]]
     Vector<Value> m_bound_arguments;                 // [[BoundArguments]]
 };
 
+template<>
+inline bool FunctionObject::fast_is<BoundFunction>() const { return is_bound_function(); }
+
 }
diff --git a/Libraries/LibJS/Runtime/FunctionObject.h b/Libraries/LibJS/Runtime/FunctionObject.h
index 78355a2ce3..5506b6ec28 100644
--- a/Libraries/LibJS/Runtime/FunctionObject.h
+++ b/Libraries/LibJS/Runtime/FunctionObject.h
@@ -42,6 +42,9 @@ public:
 
     virtual FunctionParameters const& formal_parameters() const { VERIFY_NOT_REACHED(); }
 
+    template<typename T>
+    bool fast_is() const = delete;
+
 protected:
     explicit FunctionObject(Realm&, Object* prototype, MayInterfereWithIndexedPropertyAccess = MayInterfereWithIndexedPropertyAccess::No);
     explicit FunctionObject(Object& prototype, MayInterfereWithIndexedPropertyAccess = MayInterfereWithIndexedPropertyAccess::No);
@@ -50,6 +53,7 @@ protected:
 
 private:
     virtual bool is_function() const override { return true; }
+    virtual bool is_bound_function() const { return false; }
 };
 
 template<>