diff --git a/.changeset/chilly-spiders-prove.md b/.changeset/chilly-spiders-prove.md
new file mode 100644
index 00000000..7f5f89df
--- /dev/null
+++ b/.changeset/chilly-spiders-prove.md
@@ -0,0 +1,7 @@
+---
+"partywhen": patch
+---
+
+fix: require task payload to be seralizable over RPC
+
+fixes #190
diff --git a/packages/partywhen/src/index.ts b/packages/partywhen/src/index.ts
index cf47a8b0..ba9e2945 100644
--- a/packages/partywhen/src/index.ts
+++ b/packages/partywhen/src/index.ts
@@ -4,7 +4,7 @@ import { Server } from "partyserver";
 export type RawTask = {
   id: string;
   description?: string | undefined;
-  payload?: Record<string, unknown> | undefined;
+  payload?: Record<string, Rpc.Serializable<unknown>> | undefined;
   callback?: Callback | undefined;
 } & (
   | {
diff --git a/packages/partywhen/tests/index.test.ts b/packages/partywhen/tests/index.test.ts
index ec5ced4e..1a685b9a 100644
--- a/packages/partywhen/tests/index.test.ts
+++ b/packages/partywhen/tests/index.test.ts
@@ -8,6 +8,9 @@ import { describe, expect, it } from "vitest";
 
 import worker from ".";
 
+type IsNever<T> = [T] extends [never] ? true : false;
+type AssertNot<T extends false> = T;
+
 function getStub(environment: typeof env) {
   const id = environment.SCHEDULER.idFromName("example");
   return environment.SCHEDULER.get(id);
@@ -46,6 +49,9 @@ describe("Hello World worker", () => {
       time
     });
 
+    // this will get a type error if scheduleTask returns `never`
+    type _ = AssertNot<IsNever<typeof task>>;
+
     expect(task).toMatchInlineSnapshot(`
       {
         "callback": {
@@ -123,9 +129,8 @@ describe("Hello World worker", () => {
           "test": "test",
         },
         "time": ${
-          // @ts-expect-error I'm bad at typescript
           // eslint-disable-next-line @typescript-eslint/no-unsafe-call
-          taskTime.toISOString()
+          await taskTime.toISOString()
         },
         "type": "delayed",
       }
@@ -242,11 +247,7 @@ describe("Hello World worker", () => {
         "payload": {
           "test": "test",
         },
-        "time": ${
-          // @ts-expect-error I'm bad at typescript
-          // eslint-disable-next-line @typescript-eslint/no-unsafe-call
-          time.toISOString()
-        },
+        "time": ${await time.toISOString()},
         "type": "no-schedule",
       }
     `);
@@ -268,11 +269,7 @@ describe("Hello World worker", () => {
         "description": "test",
         "id": "no-schedule-task-001",
         "payload": "{"test":"test"}",
-        "time": ${Math.floor(
-          // @ts-expect-error I'm bad at typescript
-          // eslint-disable-next-line @typescript-eslint/no-unsafe-call
-          time.getTime() / 1000
-        )},
+        "time": ${Math.floor((await time.getTime()) / 1000)},
         "type": "no-schedule",
       }
     `);