diff --git a/packages/runtime-core/src/apiWatch.ts b/packages/runtime-core/src/apiWatch.ts
index 1e5a44f5..30a76b0f 100644
--- a/packages/runtime-core/src/apiWatch.ts
+++ b/packages/runtime-core/src/apiWatch.ts
@@ -44,13 +44,7 @@ export type WatchCallback<V = any, OV = any> = (
   onInvalidate: InvalidateCbRegistrator
 ) => any
 
-type MapSources<T> = {
-  [K in keyof T]: T[K] extends WatchSource<infer V>
-    ? V
-    : T[K] extends object ? T[K] : never
-}
-
-type MapOldSources<T, Immediate> = {
+type MapSources<T, Immediate> = {
   [K in keyof T]: T[K] extends WatchSource<infer V>
     ? Immediate extends true ? (V | undefined) : V
     : T[K] extends object
@@ -93,7 +87,7 @@ export function watch<
   Immediate extends Readonly<boolean> = false
 >(
   sources: T,
-  cb: WatchCallback<MapSources<T>, MapOldSources<T, Immediate>>,
+  cb: WatchCallback<MapSources<T, false>, MapSources<T, Immediate>>,
   options?: WatchOptions<Immediate>
 ): WatchStopHandle
 
@@ -115,10 +109,10 @@ export function watch<
 ): WatchStopHandle
 
 // implementation
-export function watch<T = any>(
-  source: WatchSource<T> | WatchSource<T>[],
-  cb: WatchCallback<T>,
-  options?: WatchOptions
+export function watch<T = any, Immediate extends Readonly<boolean> = false>(
+  source: T | WatchSource<T>,
+  cb: any,
+  options?: WatchOptions<Immediate>
 ): WatchStopHandle {
   if (__DEV__ && !isFunction(cb)) {
     warn(
@@ -127,11 +121,11 @@ export function watch<T = any>(
         `supports \`watch(source, cb, options?) signature.`
     )
   }
-  return doWatch(source, cb, options)
+  return doWatch(source as any, cb, options)
 }
 
 function doWatch(
-  source: WatchSource | WatchSource[] | WatchEffect,
+  source: WatchSource | WatchSource[] | WatchEffect | object,
   cb: WatchCallback | null,
   { immediate, deep, flush, onTrack, onTrigger }: WatchOptions = EMPTY_OBJ,
   instance = currentInstance
@@ -262,11 +256,11 @@ function doWatch(
     }
   }
 
-  // important: mark the job as a watcher callback so that scheduler knows it
+  // important: mark the job as a watcher callback so that scheduler knows
   // it is allowed to self-trigger (#1727)
   job.allowRecurse = !!cb
 
-  let scheduler: (job: () => any) => void
+  let scheduler: ReactiveEffectOptions['scheduler']
   if (flush === 'sync') {
     scheduler = job
   } else if (flush === 'post') {
@@ -318,7 +312,7 @@ function doWatch(
 export function instanceWatch(
   this: ComponentInternalInstance,
   source: string | Function,
-  cb: Function,
+  cb: WatchCallback,
   options?: WatchOptions
 ): WatchStopHandle {
   const publicThis = this.proxy as any