diff --git a/types/index.test.ts b/types/index.test.ts
index cf464629..3d4de12b 100644
--- a/types/index.test.ts
+++ b/types/index.test.ts
@@ -3,7 +3,7 @@ import * as Effects from "typed-redux-saga";
 
 function* mySaga(): Effects.SagaGenerator<void> {
   yield* Effects.take("FOO"); // $ExpectType Action<any>
-  type FooAction = {type: "FOO"};
+  type FooAction = { type: "FOO" };
   yield* Effects.take<FooAction>("FOO"); // $ExpectType FooAction
   yield* Effects.takeMaybe("FOO"); // $ExpectType Action<any>
   yield* Effects.takeMaybe<FooAction>("FOO"); // $ExpectType FooAction
@@ -12,14 +12,14 @@ function* mySaga(): Effects.SagaGenerator<void> {
   yield* Effects.take(chan); // $ExpectType "FOO"
   yield* Effects.takeMaybe(chan); // $ExpectType "FOO"
 
-  yield* Effects.takeEvery("FOO", function*() {}); // $ExpectType never
-  yield* Effects.takeEvery(chan, function*() {}); // $ExpectType never
+  yield* Effects.takeEvery("FOO", function* () {}); // $ExpectType never
+  yield* Effects.takeEvery(chan, function* () {}); // $ExpectType never
 
-  yield* Effects.takeLatest("FOO", function*() {}); // $ExpectType never
-  yield* Effects.takeLatest(chan, function*() {}); // $ExpectType never
+  yield* Effects.takeLatest("FOO", function* () {}); // $ExpectType never
+  yield* Effects.takeLatest(chan, function* () {}); // $ExpectType never
 
-  yield* Effects.takeLeading("FOO", function*() {}); // $ExpectType never
-  yield* Effects.takeLeading(chan, function*() {}); // $ExpectType never
+  yield* Effects.takeLeading("FOO", function* () {}); // $ExpectType never
+  yield* Effects.takeLeading(chan, function* () {}); // $ExpectType never
 
   yield* Effects.put({ type: "FOO" }); // $ExpectType { type: string; }
   yield* Effects.put(chan, "FOO"); // $ExpectType "FOO"
@@ -27,7 +27,7 @@ function* mySaga(): Effects.SagaGenerator<void> {
   yield* Effects.putResolve({ type: "FOO" }); // $ExpectType { type: string; }
 
   // $ExpectType number
-  yield* Effects.call(function*(): SagaIterator<number> {
+  yield* Effects.call(function* (): SagaIterator<number> {
     yield* Effects.take(chan);
     return 22;
   });
@@ -48,13 +48,13 @@ function* mySaga(): Effects.SagaGenerator<void> {
   yield* Effects.cps((): number => 22);
 
   // $ExpectType FixedTask<number>
-  let task = yield* Effects.fork(function*(): SagaIterator<number> {
+  let task = yield* Effects.fork(function* (): SagaIterator<number> {
     yield* Effects.take(chan);
     return 22;
   });
 
   // $ExpectType FixedTask<number>
-  task = yield* Effects.spawn(function*(): SagaIterator<number> {
+  task = yield* Effects.spawn(function* (): SagaIterator<number> {
     yield* Effects.take(chan);
     return 22;
   });
@@ -90,30 +90,30 @@ function* mySaga(): Effects.SagaGenerator<void> {
   yield* Effects.delay(120, true);
 
   // $ExpectType never
-  yield* Effects.throttle(25, "FOO", function*(): SagaIterator<number> {
+  yield* Effects.throttle(25, "FOO", function* (): SagaIterator<number> {
     yield* Effects.take(chan);
     return 22;
   });
 
   // $ExpectType never
-  yield* Effects.debounce(25, "FOO", function*(): SagaIterator<number> {
+  yield* Effects.debounce(25, "FOO", function* (): SagaIterator<number> {
     yield* Effects.take(chan);
     return 22;
   });
 
   // $ExpectType number
-  yield* Effects.retry(5, 100, function*(): SagaIterator<number> {
+  yield* Effects.retry(5, 100, function* (): SagaIterator<number> {
     yield* Effects.take(chan);
     return 22;
   });
 
   // $ExpectType number[]
   yield* Effects.all([
-    Effects.call(function*(): Effects.SagaGenerator<number> {
+    Effects.call(function* (): Effects.SagaGenerator<number> {
       yield* Effects.take(chan);
       return 22;
     }),
-    Effects.call(function*(): Effects.SagaGenerator<number> {
+    Effects.call(function* (): Effects.SagaGenerator<number> {
       yield* Effects.take(chan);
       return 22;
     }),
@@ -121,11 +121,11 @@ function* mySaga(): Effects.SagaGenerator<void> {
 
   // $ExpectType { foo: number; bar: string; }
   yield* Effects.all({
-    foo: Effects.call(function*(): Effects.SagaGenerator<number> {
+    foo: Effects.call(function* (): Effects.SagaGenerator<number> {
       yield* Effects.take(chan);
       return 22;
     }),
-    bar: Effects.call(function*(): Effects.SagaGenerator<string> {
+    bar: Effects.call(function* (): Effects.SagaGenerator<string> {
       yield* Effects.take(chan);
       return "hello";
     }),
@@ -133,11 +133,11 @@ function* mySaga(): Effects.SagaGenerator<void> {
 
   // $ExpectType (number | undefined)[]
   yield* Effects.race([
-    Effects.call(function*(): Effects.SagaGenerator<number> {
+    Effects.call(function* (): Effects.SagaGenerator<number> {
       yield* Effects.take(chan);
       return 22;
     }),
-    Effects.call(function*(): Effects.SagaGenerator<number> {
+    Effects.call(function* (): Effects.SagaGenerator<number> {
       yield* Effects.take(chan);
       return 22;
     }),
@@ -145,13 +145,54 @@ function* mySaga(): Effects.SagaGenerator<void> {
 
   // $ExpectType { foo: number | undefined; bar: string | undefined; }
   yield* Effects.race({
-    foo: Effects.call(function*(): Effects.SagaGenerator<number> {
+    foo: Effects.call(function* (): Effects.SagaGenerator<number> {
       yield* Effects.take(chan);
       return 22;
     }),
-    bar: Effects.call(function*(): Effects.SagaGenerator<string> {
+    bar: Effects.call(function* (): Effects.SagaGenerator<string> {
       yield* Effects.take(chan);
       return "hello";
     }),
   });
+
+  // $ExpectType { type: "valid_return" };
+  yield* Effects.call(sendMessage, myMessage());
+}
+
+async function otherText() {
+  // $ExpectType { type: "valid_return" };
+  await sendMessage(myMessage());
+}
+
+export enum MessageTypes {
+  MESSAGE = "message",
+  OTHER_MESSAGE = "other_message",
+}
+
+export interface Message<T extends MessageTypes> {
+  subject: T;
+}
+
+function myMessage(): Message<MessageTypes.MESSAGE> {
+  return {
+    subject: MessageTypes.MESSAGE,
+  };
+}
+
+// Utility type for working out the message subject
+type ExtractMessage<M> = M extends Message<infer T> ? T : never;
+type IResponseTypes = { [key in MessageTypes]: unknown };
+export interface ResponseTypes extends IResponseTypes {
+  [MessageTypes.MESSAGE]: { type: "valid_return" };
+  [MessageTypes.OTHER_MESSAGE]: { type: "other_return" };
+}
+
+// Utility type to lookup the Message Response type using the messaage subject from the ResponseTypes type.
+export type Response<T extends Message<any>> = ResponseTypes[ExtractMessage<T>];
+
+export function sendMessage<M extends Message<MessageTypes>>(
+  m: M
+): Promise<Response<M>> {
+  // @ts-ignore
+  return;
 }