diff --git a/packages/nuxt/src/app/config.ts b/packages/nuxt/src/app/config.ts
index 4be4349fc4..476f828abf 100644
--- a/packages/nuxt/src/app/config.ts
+++ b/packages/nuxt/src/app/config.ts
@@ -11,6 +11,15 @@ type DeepPartial<T> = T extends Function ? T : T extends Record<string, any> ? {
 // Workaround for vite HMR with virtual modules
 export const _getAppConfig = () => __appConfig as AppConfig
 
+function isPojoOrArray (val: unknown): val is object {
+  return (
+    Array.isArray(val) ||
+    (!!val &&
+      typeof val === 'object' &&
+      val.constructor?.name === 'Object')
+  )
+}
+
 function deepDelete (obj: any, newObj: any) {
   for (const key in obj) {
     const val = newObj[key]
@@ -18,7 +27,7 @@ function deepDelete (obj: any, newObj: any) {
       delete (obj as any)[key]
     }
 
-    if (val !== null && typeof val === 'object') {
+    if (isPojoOrArray(val)) {
       deepDelete(obj[key], newObj[key])
     }
   }
@@ -27,7 +36,7 @@ function deepDelete (obj: any, newObj: any) {
 function deepAssign (obj: any, newObj: any) {
   for (const key in newObj) {
     const val = newObj[key]
-    if (val !== null && typeof val === 'object') {
+    if (isPojoOrArray(val)) {
       const defaultVal = Array.isArray(val) ? [] : {}
       obj[key] = obj[key] || defaultVal
       deepAssign(obj[key], val)
diff --git a/test/nuxt/composables.test.ts b/test/nuxt/composables.test.ts
index bd8865d028..364279f7eb 100644
--- a/test/nuxt/composables.test.ts
+++ b/test/nuxt/composables.test.ts
@@ -33,23 +33,33 @@ registerEndpoint('/api/test', defineEventHandler(event => ({
 describe('app config', () => {
   it('can be updated', () => {
     const appConfig = useAppConfig()
-    expect(appConfig).toMatchInlineSnapshot(`
-      {
-        "nuxt": {},
-      }
-    `)
-    updateAppConfig({
+    expect(appConfig).toStrictEqual({ nuxt: {} })
+
+    type UpdateAppConfig = Parameters<typeof updateAppConfig>[0]
+
+    const initConfig: UpdateAppConfig = {
       new: 'value',
       nuxt: { nested: 42 },
+      regExp: /foo/g,
+      date: new Date(1111, 11, 11),
+      arr: [1, 2, 3],
+    }
+    updateAppConfig(initConfig)
+    expect(appConfig).toStrictEqual(initConfig)
+
+    const newConfig: UpdateAppConfig = {
+      nuxt: { anotherNested: 24 },
+      regExp: /bar/g,
+      date: new Date(2222, 12, 12),
+      arr: [4, 5],
+    }
+    updateAppConfig(newConfig)
+    expect(appConfig).toStrictEqual({
+      ...initConfig,
+      ...newConfig,
+      nuxt: { ...initConfig.nuxt, ...newConfig.nuxt },
+      arr: [4, 5, 3],
     })
-    expect(appConfig).toMatchInlineSnapshot(`
-      {
-        "new": "value",
-        "nuxt": {
-          "nested": 42,
-        },
-      }
-    `)
   })
 })