diff --git a/packages/nuxt/src/app/config.ts b/packages/nuxt/src/app/config.ts
index 14b63c0739..f0e653fc6f 100644
--- a/packages/nuxt/src/app/config.ts
+++ b/packages/nuxt/src/app/config.ts
@@ -35,6 +35,7 @@ function deepDelete (obj: any, newObj: any) {
 
 function deepAssign (obj: any, newObj: any) {
   for (const key in newObj) {
+    if (key === '__proto__' || key === 'constructor') { continue }
     const val = newObj[key]
     if (isPojoOrArray(val)) {
       const defaultVal = Array.isArray(val) ? [] : {}