diff --git a/src/core.ts b/src/core.ts
index acb6c3a..c1de918 100644
--- a/src/core.ts
+++ b/src/core.ts
@@ -1,5 +1,6 @@
 import { createReactiveSystem, Dependency, Link, Subscriber, SubscriberFlags } from 'alien-signals';
 import { ReactiveFlags } from "./contents"
+import { isFunction } from './utils';
 const {
   link,
   propagate,
@@ -238,9 +239,6 @@ export function unSignal<T>(signal: MaybeSignal<T> | Computed<T>): T {
   return (isSignal(signal) ? signal.value : signal) as T;
 }
 
-export const isFunction = (val: unknown): val is Function =>
-  typeof val === 'function'
-
 export function toValue<T>(source: MaybeSignalOrGetter<T>): T {
   return isFunction(source) ? source() : unSignal(source)
 }
diff --git a/src/index.ts b/src/index.ts
index 3b1191d..148516e 100644
--- a/src/index.ts
+++ b/src/index.ts
@@ -1,3 +1,16 @@
 export * from "./core";
 export * from "./deepSignal";
 export * from "./watch"
+export {
+  isArray,
+  isDate,
+  isFunction,
+  isMap,
+  isObject,
+  isPlainObject,
+  isPromise,
+  isRegExp,
+  isSet,
+  isString,
+  isSymbol,
+} from "./utils"
diff --git a/src/utils.ts b/src/utils.ts
index 5c45714..6e927f8 100644
--- a/src/utils.ts
+++ b/src/utils.ts
@@ -37,3 +37,5 @@ export const isPlainObject = (val: unknown): val is object =>
 
 export const hasChanged = (value: any, oldValue: any): boolean =>
   !Object.is(value, oldValue)
+
+export function NOOP() {}
diff --git a/src/watch.ts b/src/watch.ts
index 19d2a67..f4a3fb0 100644
--- a/src/watch.ts
+++ b/src/watch.ts
@@ -1,5 +1,5 @@
 import { Computed, Effect, isSignal, Signal } from './core';
-import { hasChanged, isArray, isMap, isObject, isPlainObject, isSet } from './utils';
+import { hasChanged, isArray, isMap, isObject, isPlainObject, isSet, NOOP } from './utils';
 import { isDeepSignal, isShallow } from "./deepSignal"
 import { ReactiveFlags } from './contents';
 
@@ -69,9 +69,7 @@ export function watch(
     getter = () => source.value
     forceTrigger = isShallow(source)
   } else if (isDeepSignal(source)) {
-    getter = () => {
-      return signalGetter(source)
-    }
+    getter = () => signalGetter(source)
     forceTrigger = true
   } else if (isArray(source)) {
     isMultiSource = true
@@ -85,6 +83,14 @@ export function watch(
         }
       })
   }
+  else {
+    getter = NOOP
+    if (process.env.NODE_ENV !== 'production') {
+      console.warn(
+        'Invalid watch source. Source must be a signal, a computed value !',
+      )
+    }
+  }
   if (cb && deep) {
     const baseGetter = getter
     const depth = deep === true ? Infinity : deep