--- a/src/types.ts
+++ b/src/types.ts
@@ -32,8 +32,8 @@ type TransformMethod<T> = (event: EmitterWebhookEvent) => T | PromiseLike<T>;
 
 export type HandlerFunction<
   TName extends EmitterWebhookEventName,
-  TTransformed
-> = (event: EmitterWebhookEvent<TName> & TTransformed) => any;
+  TTransform
+> = (event: TTransform extends TransformMethod<infer T> ? T : EmitterWebhookEvent<TName>) => any;
 
 type Hooks = {
   [key: string]: Function[];

--- a/test/integration/event-handler-test.ts
+++ b/test/integration/event-handler-test.ts
@@ -131,15 +131,15 @@ test("options.transform", (done) => {
   const eventHandler = createEventHandler({
     transform: (event) => {
       expect(event.id).toBe("123");
       return "funky";
     },
   });
 
-  eventHandler.on("push", (event: EmitterWebhookEvent) => {
+  eventHandler.on("push", (event: string) => {
     expect(event).toBe("funky");
 
     done();