diff --git a/src/actions.test.todo b/src/actions.test.todo
index c442f36..d1e45ee 100644
--- a/src/actions.test.todo
+++ b/src/actions.test.todo
@@ -4,16 +4,6 @@ import { action } from './actions.js';
 
 import { Updux } from './Updux.js';
 
-test('basic action', () => {
-    const foo = action('foo', (thing) => ({ thing }));
-
-    expect(foo('bar')).toEqual({
-        type: 'foo',
-        payload: {
-            thing: 'bar',
-        },
-    });
-});
 
 test('Updux config accepts actions', () => {
     const foo = new Updux({
diff --git a/src/actions.test.ts b/src/actions.test.ts
index 76cdb07..c051266 100644
--- a/src/actions.test.ts
+++ b/src/actions.test.ts
@@ -1,4 +1,18 @@
-import Updux, { createAction } from './index.js';
+import Updux, { createAction, withPayload } from './index.js';
+
+test('basic action', () => {
+    const foo = createAction(
+        'foo',
+        withPayload((thing: string) => ({ thing })),
+    );
+
+    expect(foo('bar')).toEqual({
+        type: 'foo',
+        payload: {
+            thing: 'bar',
+        },
+    });
+});
 
 test('subduxes actions', () => {
     const bar = createAction<number>('bar');
diff --git a/src/actions.ts b/src/actions.ts
index d36171b..9bd5453 100644
--- a/src/actions.ts
+++ b/src/actions.ts
@@ -2,6 +2,14 @@ import { createAction } from '@reduxjs/toolkit';
 
 export { createAction } from '@reduxjs/toolkit';
 
-export const withPayload =
-    <P>() =>
-    (payload: P) => ({ payload });
+interface WithPayload {
+    (): <P>(input: P) => { payload: P };
+    <P, A extends any[]>(prepare: (...args: A) => P): (...input: A) => {
+        payload: P;
+    };
+}
+
+export const withPayload: WithPayload = ((prepare) =>
+    (...input) => ({
+        payload: prepare ? prepare(...input) : input,
+    })) as any;