diff --git a/Libraries/LibWeb/WebIDL/Promise.cpp b/Libraries/LibWeb/WebIDL/Promise.cpp
index c25a420ff5e..d2865b5644b 100644
--- a/Libraries/LibWeb/WebIDL/Promise.cpp
+++ b/Libraries/LibWeb/WebIDL/Promise.cpp
@@ -333,4 +333,10 @@ GC::Ref<Promise> create_rejected_promise_from_exception(JS::Realm& realm, Except
     return WebIDL::create_rejected_promise(realm, throw_completion.value());
 }
 
+void reject_promise_with_exception(JS::Realm& realm, Promise const& promise, Exception exception)
+{
+    auto throw_completion = Bindings::exception_to_throw_completion(realm.vm(), move(exception));
+    WebIDL::reject_promise(realm, promise, throw_completion.value());
+}
+
 }
diff --git a/Libraries/LibWeb/WebIDL/Promise.h b/Libraries/LibWeb/WebIDL/Promise.h
index 8a6b1acbe71..9efce82c9bf 100644
--- a/Libraries/LibWeb/WebIDL/Promise.h
+++ b/Libraries/LibWeb/WebIDL/Promise.h
@@ -34,7 +34,8 @@ WEB_API bool is_promise_fulfilled(Promise const&);
 WEB_API void wait_for_all(JS::Realm&, ReadonlySpan<GC::Ref<Promise>> promises, Function<void(Vector<JS::Value> const&)> success_steps, Function<void(JS::Value)> failure_steps);
 WEB_API GC::Ref<Promise> get_promise_for_wait_for_all(JS::Realm&, ReadonlySpan<GC::Ref<Promise>> promises);
 
-// Non-spec, convenience method.
+// Non-spec, convenience methods.
 WEB_API GC::Ref<Promise> create_rejected_promise_from_exception(JS::Realm&, Exception);
+WEB_API void reject_promise_with_exception(JS::Realm&, Promise const&, Exception);
 
 }